I built a desk each for my son and daughter. They got to choose the type of base. I used old bed slats 90x45mm (4x2) salvaged from verge ripped in half for the bases. I used 12mm plywood for the tops. 7mm ply for the shelves on the sawhorse leg version. Unfortunately, despite getting the straightest and flattest plywood available and subjecting it to all sorts of manipulation, a couple of the flip-top sections are warped to there are slight gaps on one side.
I modified the plan so that the middle section could lift up as well. The back 1x3 of the storage section extended the full width.