_blocks.scss

.wp-block-button {
	margin-bottom: $base-margin;
	text-align: center;
	
	.wp-block-button__link {
		@extend %button;
	}
}

_placeholders.scss

%button {
	background: $highlight;
	border: none;
	border-radius: 4px;
	box-shadow: none;
	color: $white;
	cursor: pointer;
	padding: 10px;
	text-align: center;
	text-decoration: none;
	width: auto;
	-webkit-appearance: none;

	&:hover {
		background-color: darken( $highlight, 10%);
		color: $white;
		text-decoration: none;		
	}
}