Just used some clear pine 1 x 4 planks, but the pieces and glued and screwed them together. I finished the end result to match the existing cabinet. Then I used screws and nuts to fasten them to the side of the existing cabinet. It can be taken out as easily as unbolting four screws, leaving only four small holes in the existing cabinet. The shelves under the window are actually two serving trays I found at Big Lots, which just fit tightly. I put rubberized placemats under them to keep them intact and additional rubberized placemats in the bottoms to keep everything in place. Nothing has ever spilled out. I was camped over a weekend earlier, and happened upon another Flagstaff like mine. I showed them the modification and he contracted me to make him one. So, you may see another one pop up on this board. It really gives a lot more storage when setup.