I actually went to my uncle for cutting the 4 pieces, as I originally just wanted a collar on top, and planned on laying the freezer lid on top of the collar. I live in an apartment and have limited access to tools, and figured he'd be much better to go to since he's works in cabinetry, than the guy from Home Depot who didn't understand the board measurements I gave him. Anyways, when I went to pick up the cut beams, a fully enclosed and insulated lid awaited me (he always goes above and beyond - he's awesome). The lid looks to me like it was all glued together as I can't make out any nail holes. So I'm guessing he used just a strong wood glue and some grips to hold it all together. The board insulation is screwed into the wood from the inside, and the whole lid is attached to the freezer using the original hinges. My only hiccup was that I attached the lid without removing the temp controller wire, so there is this very slight gradient towards the hinges, but nothing crazy. A thin gasket around the lip would probably take care of that.
All in it's been working great so far. It doesn't seem to cycle much and the beer has been tasty. Now to refill my co2....again