On iPad allows you to present a view controller in a form sheet with regular/regular traits

BTFormSheetViewController.h

//
//  BTFormSheetViewController.h
//
//  Created by Cameron Cooke on 18/09/2015.
//  Copyright © 2015 Brightec. All rights reserved.
//
//  Licensed under the Apache License, Version 2.0 (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//  http://www.apache.org/licenses/LICENSE-2.0
//
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS,
//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//  See the License for the specific language governing permissions and
//  limitations under the License.
//

#import <UIKit/UIKit.h>

@interface BTFormSheetViewController : UIViewController
- (instancetype)initWithClassToInsantiate:(Class)targetClass embedInNavigationController:(BOOL)embeded;
@end

BTFormSheetViewController.m

//
//  BTFormSheetViewController.m
//
//  Created by Cameron Cooke on 18/09/2015.
//  Copyright © 2015 Brightec. All rights reserved.
//
//  Licensed under the Apache License, Version 2.0 (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//  http://www.apache.org/licenses/LICENSE-2.0
//
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS,
//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//  See the License for the specific language governing permissions and
//  limitations under the License.
//

#import "BTFormSheetViewController.h"


@interface BTFormSheetViewController ()
@property (assign, nonatomic) Class targetClass;
@property (assign, nonatomic) BOOL embeded;
@end


@implementation BTFormSheetViewController


- (instancetype)initWithClassToInsantiate:(Class)targetClass embedInNavigationController:(BOOL)embeded
{
    self = [super init];
    if (self) {
        
        NSAssert([targetClass isSubclassOfClass:[UIViewController class]], @"Class must be a decendent of UIViewController");
        
        _embeded = embeded;
        _targetClass = targetClass;
    }
    return self;
}


- (void)viewDidLoad
{
    [super viewDidLoad];
    [self setupRootView];
}


- (void)setupRootView
{
    self.view = [[UIView alloc] initWithFrame:[UIScreen mainScreen].bounds];
    
    UIViewController *controller;
    if (self.embeded) {
        UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:[self.targetClass new]];
        controller = (UIViewController *)navController;
    } else {
        controller = [self.targetClass new];
    }
    
    [self addChildViewController:controller];
    [self.view addSubview:controller.view];
    controller.view.translatesAutoresizingMaskIntoConstraints = NO;
    
    NSDictionary *viewsDictionary = @{@"view": controller.view};
    NSArray *horizontalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"H:[view]" options:0 metrics:nil views:viewsDictionary];
    [self.view addConstraints:horizontalConstraints];
    
    NSArray *verticalConstraints = [NSLayoutConstraint constraintsWithVisualFormat:@"V:[view]" options:0 metrics:nil views:viewsDictionary];
    [self.view addConstraints:verticalConstraints];    
    
    [controller didMoveToParentViewController:self];
}


- (UITraitCollection *)overrideTraitCollectionForChildViewController:(UIViewController *)childViewController
{
    UITraitCollection *horizontalRegular = [UITraitCollection traitCollectionWithHorizontalSizeClass:UIUserInterfaceSizeClassRegular];
    UITraitCollection *verticalRegular = [UITraitCollection traitCollectionWithVerticalSizeClass:UIUserInterfaceSizeClassRegular];
    
    return [UITraitCollection traitCollectionWithTraitsFromCollections:@[self.traitCollection, horizontalRegular, verticalRegular]];
}


- (void)setOverrideTraitCollection:(UITraitCollection *)collection forChildViewController:(UIViewController *)childViewController
{
    [self overrideTraitCollectionForChildViewController:childViewController];
}


@end

We use the container view controller protocol to embed the target view controller and override the trait collection to be regular height regular width.