I've made a few cases for lap dulcimers, and a much more complex one for a 4-string banjo, and must warn would-be DIYers that, at least in my area, it's very difficult to find appropriate wood for cases for instruments of significant size, unless you're young and husky.

Getting something sturdy enough to protect the instrument that doesn't weigh "tons" (relative to the instrument) is - IMO - the toughest part of the task.

Hinges and latches are fairly easy to find and not too expensive, but local sources offer only "structural" weights in plywood. Wood veneer, the only thinner stuff available isn't very resistant to "puncture wounds" and "composites" like masonite (or counter top laminates) are incredibly "dense."

The "apparent weight" can be made less objectionable if you make the box first, and then select an appropriate handle. For a decently sturdy case that comes out even a bit heavy, you need a handle that you can get all four fingers through up to the first knuckles.

Carrying even 8 or 10 pounds with just your fingertips gets annoying rather rapidly, so drawer pulls and such usually end up being a bit too small for comfort. Gate handles may be more appropriate, even if they're not so pretty. True "luggage handles" would perhaps be nicer, but in my area at least they tend to be a bit expensive if your purpose in building your own is to save money.

"Cardboardish" materials and even "masonite panel" stock can be bent using the same heat/steam methods as for wood, but require a bit of "extra care" and more gentle "working" of the bend; and they're among the materials that often end up as a heavier box than you'd like.

John