I thought a bit about the hinge pin. For this one I decided to leave it visible. It's 3/16 brass rod. I hadn't thought of using a plug to hide it. Might try that on the next one . . . or I might try to drill the hole part way through from the inside and trap the hinge pin inside. That could be a little tricky.
The bottom is 1/4 ply with a BEM veneer. I got a bunch of it for cheap a couple of years ago. It's a bit wavey but it flattens out OK. I just glue it up good, sandwich it between a couple of pieces of MDF, sit my planer on top and let it sit overnight.
pete