Buy some full sheets of drywall.

Ohh I thought height was the issue, nm. Yes you want both pieces to end on a stud.

Or just make an inconvenient window or door.

I'd keep the seem as low as possible (so go 24 +8 with 8 at the bottom) for two reasons:

If your spackle and paint aren't up to par the seem is below eye level and likely to be covered by furniture.

Two, in the event that damage to drywall is done its usually at arm/elbow height (not going to matter either way) or really low - this makes replacing it easier if you can take out the are between boards and replace it smoothly without having to cut around the sheet (if its too big to just spackle).

A wooden stud. Not you.

I don't want to see a post later saying "Help! Drywall screws in my junk!"

Wouldn't that be a convenient window or door?

Ok to clarify, the height of the drywall will be ~10 inches so seem height is not the problem, nor elbows, etc. Kicks could be though.

Essentially it is an unfinished step that leads into the crawl space in the attic.

The walls around it are drywall so actual wood would look off. Once I've drywalled the step I am going to put in a door to replace the fancy curtain the previous owner had hung there

If you absolutely insist the riser look like the walls in color and texture, you can put a thin l layer of mud over the wood and lightly sand it to fill any visible grain lines and make the painted surface identical to the wall near it.

Drywall would cut it, or plywood, as long as you have a piece with a nice side, fill, sand, work complete, outside of the finish. Can you turn either of the pieces of drywall you have sideways and cut it to height?

Yeh, just rock it and caulk it.

Ezpz.