I prefer a two layer table, MDF on the bottom, VERY VERY flat ply on top, carefully glued together along with screws. Cut the full opening in the top sheet (use half inch Baltic Birch if you can find it). Cut a smaller opening in the bottom layer to form a lip, then pre-drill openings for your leveling screws to go in. You could also use threaded inserts, but not necessary.
The other leveling option is easier. Order a set of Kreg leveling screws that fit in the corner of your opening, about $20 a set of 4. You can do this with a single layer table as well, but If you can, add that second layer, it will hold screws better over time. Wax and polish the top with a powered buffer, not by hand. Here's a pix of the Kreg leveling screws. It shows a rounded corner but will work as well with a sharp, 90 degree corner.
Many folks would prefer a laminate top. If you do that, you'll want to roll on contact cement as smooth as you can, let it dry then use dowels or sticks to hold the top and laminate apart. Once they touch, they are glued forever. You pull dowels or sticks out one at a time, press that section down with a roller, starting from the center, out to avoid trapping air bubbles. Remove another dowel, roll from the already flat outward and center to the edge. Once down flat, you'll use a trim bit to cut off the excess. If you trapped an air bubble, use a small drill bit with a stop so it penetrates the base, but not the laminate. Measure carefully to locate the center of the air bubble, drill and let the air out, then roll it flat. Cut your openings before you apply the laminate.
But ample, polished wax will do.
The more I do, the less I accomplish.
Last edited by DesertRatTom; 02-24-2019 at 01:10 PM.