Do you plan to have anything underneath the bed, like drawers?

If so, I would build boxes (cabinets) with drawer slides, either 3 at just under 20", or 2 at 30". Then I would tie the boxes together but not anchor them to the wall. I would also use baltic birch plywood no matter what design you use.

That sound great, thank you, Michelle! Then the next owners can adjust the size.

I built one for my daughter. I realize your dimensions are not the same as mine, but the pics may help you visualize the process. Her bed is a full-size mattress.

Captions are under each picture.

This shows the framing. Birch plywood. One large box underneath...six drawers in the center (3 over 3) and a cabinet on each end. Bookshelves at the head and foot of the bed.

The front of the bed. She calls it the "Mousehole Bed". The lighter rectangle in the middle of the front that contains the opening is removable.

Painted up with the kids inside.

Raised panels on the back wall, along with two wall sconces.

Bookshelves at the foot of the bed.

A reading niche with bookshelves on each side at the head of the bed. The exposed wire on the right side of the niche has since been run behind the woodwork, it's a low voltage wire to dim the reading lights above.

The ceiling inside the bed is a beadboard-type that I made from scraps. The shelf and the shelf support above the opening are the waste cutoffs from when I cut the arched ribs to back the arched beadboard ceiling.

Thank you, Mongo! I'm going to do it soon and just looked this topic up, almost a year later, and found these great pictures.