all you need to do is put in a couple 2x12's perpendicular to the ones you already have in place to sort of make a box and the door is the top of it. I'm too old and a little to fat to crawl in under my trap door to take a picture so hope this description helps.
if you want to make the door from an edge of the room then you only need to add one 2x12 and i'm guessing your joists are 12 or 16 inch on center so there should be plenty of room to screw in or nail the new 2x12 in place from the sides.
I gotcha, a box cut in the joists and the subfloor cut back a bit so that the trap door just rests on the joists.
Will have to think about that some more. Not sure it'll be worth it if only because I won't fit in the space!

It's not about being fat, it's about size. I'm 6'2" and although that's not that tall, 11" of clearance is wicked tight. Tried it out yesterday and decided I'd rather tear out the floor than do that again, so I floored it in, no access hatch. Worst case scenario, I can cut a hole in the floor and put one in later down the line.


