You won't be able to, as an upholstered seat, will hit the upholstered back, and prevent an adequate lift. Either do a loose bench cushion only, or don't make the storage. Frankly...........it's very INCONVENIENT storage in the best scenario

A better alternative would be drawers built to open from the front.

We had a breakfast nook 2 piece L shaped bench built for our sunroom (see photos) and opted for a removable back cushion on the long side and just use pillows when we need them on the short side. I agree it is inconvenient storage but it is perfect to store things you don't use often. We didn't have room for drawers. The entire unit is movable in case we move or want to reconfigure at a later date and the back cushion leans easily against the wall since it is a slight wedge shape- doesn't budge unless it is lifted off.