I once had a futon bed (the flat kind, not the folding kind) that looked a lot like that.

Something along these lines:

It's called a floating platform bed. You can find them with or without headboards on Amazon if you're willing to pay an arm and a leg, or diy one. YouTube has a few tutorials

I would never have one without the headboard .

You can get platforms anywhere. West Elm for instance. But I guarantee you'll be pillow grabbing all night. The frame always extends past the mattress. Otherwise it known as a bed . Low to the ground perhaps, but not a "platform" You may as well put the mattress on the darn floor and call it a day. Or build your own "box" with no legs, to any height off the floor you would like to BE. Get the plywood. : )

I am currently renting a unit during my remodel and learning how uncomfortable certain things can be that I never thought about it.

There is NO headboard on the bed and it is indeed uncomfortable for anything buy lying flat on the back.

Also the damn mattress slides all over the place so it have to shove it back into place at least once a day.

There are minimal looking headboards that supply more utility and comfort.