Change WooCommerce variations layout https://www.damiencarbery.com/2017/11/change-woocommerce-variations-layout/

variable-new-layout.php

<?php
/**
 * Variable product add to cart
 *
 * This template can be overridden by copying it to yourtheme/woocommerce/single-product/add-to-cart/variable.php.
 *
 * HOWEVER, on occasion WooCommerce will need to update template files and you
 * (the theme developer) will need to copy the new files to your theme to
 * maintain compatibility. We try to do this as little as possible, but it does
 * happen. When this occurs the version of the template file will be bumped and
 * the readme will list any important changes.
 *
 * @see 	https://docs.woocommerce.com/document/template-structure/
 * @author  WooThemes
 * @package WooCommerce/Templates
 * @version 2.5.0
 */
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

global $product;

$attribute_keys = array_keys( $attributes );

do_action( 'woocommerce_before_add_to_cart_form' ); ?>

<form class="variations_form cart" method="post" enctype='multipart/form-data' data-product_id="<?php echo absint( $product->id ); ?>" data-product_variations="<?php echo htmlspecialchars( json_encode( $available_variations ) ) ?>">
	<?php do_action( 'woocommerce_before_variations_form' ); ?>

	<?php if ( empty( $available_variations ) && false !== $available_variations ) : ?>
		<p class="stock out-of-stock"><?php _e( 'This product is currently out of stock and unavailable.', 'woocommerce' ); ?></p>
	<?php else : ?>
		<table class="variations" cellspacing="0">
			<tbody>
			<?php $labels = $values = ''; ?>
				<?php foreach ( $attributes as $attribute_name => $options ) : ?>
					<!--<tr>-->
					<?php ob_start(); ?>
						<td class="label"><label for="<?php echo sanitize_title( $attribute_name ); ?>"><?php echo wc_attribute_label( $attribute_name ); ?></label><?php if (( class_exists('YITH_WCPSC_Frontend_Premium') ) && ('Size' == wc_attribute_label( $attribute_name ))) { YITH_WCPSC_Frontend_Premium::get_instance()->print_button(); } ?></td>
						<?php $labels .= ob_get_contents(); ob_end_clean(); ?>
						<?php ob_start(); ?>
						<td class="value">
							<?php
								$selected = isset( $_REQUEST[ 'attribute_' . sanitize_title( $attribute_name ) ] ) ? wc_clean( urldecode( $_REQUEST[ 'attribute_' . sanitize_title( $attribute_name ) ] ) ) : $product->get_variation_default_attribute( $attribute_name );
								wc_dropdown_variation_attribute_options( array( 'options' => $options, 'attribute' => $attribute_name, 'product' => $product, 'selected' => $selected ) );
								echo end( $attribute_keys ) === $attribute_name ? apply_filters( 'woocommerce_reset_variations_link', '<a class="reset_variations" href="#">' . __( 'Clear', 'woocommerce' ) . '</a>' ) : '';
							?>
						</td>
						<?php $values .= ob_get_contents(); ob_end_clean(); ?>
					<!--</tr>-->
				<?php endforeach;?>
				<?php echo '<tr>', $labels, '<td>Qty</td>', '</tr><tr>', $values, '<td>', woocommerce_quantity_input( array( 'input_value' => isset( $_POST['quantity'] ) ? wc_stock_amount( $_POST['quantity'] ) : 1 ) ), '</td>', '</tr>'; ?>
			</tbody>
		</table>

		<?php do_action( 'woocommerce_before_add_to_cart_button' ); ?>

		<div class="single_variation_wrap">
			<?php
				/**
				 * woocommerce_before_single_variation Hook.
				 */
				do_action( 'woocommerce_before_single_variation' );

				/**
				 * woocommerce_single_variation hook. Used to output the cart button and placeholder for variation data.
				 * @since 2.4.0
				 * @hooked woocommerce_single_variation - 10 Empty div for variation data.
				 * @hooked woocommerce_single_variation_add_to_cart_button - 20 Qty and cart button.
				 */
				do_action( 'woocommerce_single_variation' );

				/**
				 * woocommerce_after_single_variation Hook.
				 */
				do_action( 'woocommerce_after_single_variation' );
			?>
		</div>

		<?php do_action( 'woocommerce_after_add_to_cart_button' ); ?>
	<?php endif; ?>

	<?php do_action( 'woocommerce_after_variations_form' ); ?>
</form>

<?php
do_action( 'woocommerce_after_add_to_cart_form' );

variable.diff

--- variable.php	2017-01-18 17:27:34.000000000 +0000
+++ variable.new.php	2017-11-05 22:11:51.902289800 +0000
@@ -33,9 +33,13 @@
 	<?php else : ?>
 		<table class="variations" cellspacing="0">
 			<tbody>
+			<?php $labels = $values = ''; ?>
 				<?php foreach ( $attributes as $attribute_name => $options ) : ?>
-					<tr>
-						<td class="label"><label for="<?php echo sanitize_title( $attribute_name ); ?>"><?php echo wc_attribute_label( $attribute_name ); ?></label></td>
+					<!--<tr>-->
+					<?php ob_start(); ?>
+						<td class="label"><label for="<?php echo sanitize_title( $attribute_name ); ?>"><?php echo wc_attribute_label( $attribute_name ); ?></label><?php if (( class_exists('YITH_WCPSC_Frontend_Premium') ) && ('Size' == wc_attribute_label( $attribute_name ))) { YITH_WCPSC_Frontend_Premium::get_instance()->print_button(); } ?></td>
+						<?php $labels .= ob_get_contents(); ob_end_clean(); ?>
+						<?php ob_start(); ?>
 						<td class="value">
 							<?php
 								$selected = isset( $_REQUEST[ 'attribute_' . sanitize_title( $attribute_name ) ] ) ? wc_clean( urldecode( $_REQUEST[ 'attribute_' . sanitize_title( $attribute_name ) ] ) ) : $product->get_variation_default_attribute( $attribute_name );
@@ -43,8 +47,10 @@
 								echo end( $attribute_keys ) === $attribute_name ? apply_filters( 'woocommerce_reset_variations_link', '<a class="reset_variations" href="#">' . __( 'Clear', 'woocommerce' ) . '</a>' ) : '';
 							?>
 						</td>
-					</tr>
+						<?php $values .= ob_get_contents(); ob_end_clean(); ?>
+					<!--</tr>-->
 				<?php endforeach;?>
+				<?php echo '<tr>', $labels, '<td>Qty</td>', '</tr><tr>', $values, '<td>', woocommerce_quantity_input( array( 'input_value' => isset( $_POST['quantity'] ) ? wc_stock_amount( $_POST['quantity'] ) : 1 ) ), '</td>', '</tr>'; ?>
 			</tbody>
 		</table>
 

variable.php

<?php
/**
 * Variable product add to cart
 *
 * This template can be overridden by copying it to yourtheme/woocommerce/single-product/add-to-cart/variable.php.
 *
 * HOWEVER, on occasion WooCommerce will need to update template files and you
 * (the theme developer) will need to copy the new files to your theme to
 * maintain compatibility. We try to do this as little as possible, but it does
 * happen. When this occurs the version of the template file will be bumped and
 * the readme will list any important changes.
 *
 * @see 	https://docs.woocommerce.com/document/template-structure/
 * @author  WooThemes
 * @package WooCommerce/Templates
 * @version 2.5.0
 */
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

global $product;

$attribute_keys = array_keys( $attributes );

do_action( 'woocommerce_before_add_to_cart_form' ); ?>

<form class="variations_form cart" method="post" enctype='multipart/form-data' data-product_id="<?php echo absint( $product->id ); ?>" data-product_variations="<?php echo htmlspecialchars( json_encode( $available_variations ) ) ?>">
	<?php do_action( 'woocommerce_before_variations_form' ); ?>

	<?php if ( empty( $available_variations ) && false !== $available_variations ) : ?>
		<p class="stock out-of-stock"><?php _e( 'This product is currently out of stock and unavailable.', 'woocommerce' ); ?></p>
	<?php else : ?>
		<table class="variations" cellspacing="0">
			<tbody>
				<?php foreach ( $attributes as $attribute_name => $options ) : ?>
					<tr>
						<td class="label"><label for="<?php echo sanitize_title( $attribute_name ); ?>"><?php echo wc_attribute_label( $attribute_name ); ?></label></td>
						<td class="value">
							<?php
								$selected = isset( $_REQUEST[ 'attribute_' . sanitize_title( $attribute_name ) ] ) ? wc_clean( urldecode( $_REQUEST[ 'attribute_' . sanitize_title( $attribute_name ) ] ) ) : $product->get_variation_default_attribute( $attribute_name );
								wc_dropdown_variation_attribute_options( array( 'options' => $options, 'attribute' => $attribute_name, 'product' => $product, 'selected' => $selected ) );
								echo end( $attribute_keys ) === $attribute_name ? apply_filters( 'woocommerce_reset_variations_link', '<a class="reset_variations" href="#">' . __( 'Clear', 'woocommerce' ) . '</a>' ) : '';
							?>
						</td>
					</tr>
				<?php endforeach;?>
			</tbody>
		</table>

		<?php do_action( 'woocommerce_before_add_to_cart_button' ); ?>

		<div class="single_variation_wrap">
			<?php
				/**
				 * woocommerce_before_single_variation Hook.
				 */
				do_action( 'woocommerce_before_single_variation' );

				/**
				 * woocommerce_single_variation hook. Used to output the cart button and placeholder for variation data.
				 * @since 2.4.0
				 * @hooked woocommerce_single_variation - 10 Empty div for variation data.
				 * @hooked woocommerce_single_variation_add_to_cart_button - 20 Qty and cart button.
				 */
				do_action( 'woocommerce_single_variation' );

				/**
				 * woocommerce_after_single_variation Hook.
				 */
				do_action( 'woocommerce_after_single_variation' );
			?>
		</div>

		<?php do_action( 'woocommerce_after_add_to_cart_button' ); ?>
	<?php endif; ?>

	<?php do_action( 'woocommerce_after_variations_form' ); ?>
</form>

<?php
do_action( 'woocommerce_after_add_to_cart_form' );