Add Scroll View with constraints well defined for keyboard extension

I need help to create a working scroll view that has some 20 buttons diplayed in two rows for the storyboard of a custom keyboard extension and that the user can horizontal scroll trough them. I'll use this github for the keyboard: [login to view URL] If you look inside the extension code/storyboard there's 3 rows views for the letters and a fourth row view. My ideia is to create a view with a scrollview inside ocuppying those 3 rows views size and this new view would show above all others. We only need to hide the other views. Inside the scroll view i want two rows of buttons that later i'll change to emojis. All needed code to change between the scroll view and the other views on the storyboard can be leave aside for now. I'll take care of that. My problem is that i'm not good with constraints and i'm having a huge headache making this view work. Some ideias of what i want to achieve can be found in the keyboard of this app: [login to view URL] Below i leave pictures of how the template keyboad looks, the app that has the emoji displayed like i want and where i want the scroll view display on the template keyboard. Thanks.