How to control layout of posts on page?

I think it’s a very reasonable ‘ask’ for WordPress. If it were me, I’d use Advanced Custom Fields for this, and set up some fields on the homepage so that the user can easily choose the relevant posts they want to show on those spots. You can call them Spot A, Spot B, or whatever you want.

I’d set these up using the ACF Post Object field.

Once you’ve set these up, the user can choose the relevant post from an easy list (see below – however you’d just limit it to posts and not show pages and attachments etc).

In your backend, you then look for the relevant chosen post object to show.

Of course, there are myriad other ways, including tags etc. However, the tags will have some tricks and hurdles, and – to put it bluntly – can more easily be ‘stuffed up’ by your client.

Good luck, and let us know how you go!