I threw mine together with 2x4s and 1/2" plywood.
It’s not fancy at all, and all I did was shim the spoil board to take out some of the bigger dips and make surfacing easier.
The CNC cut parametric tables are nice and take a lot of the guess work out of sizing etc if the calculators are nice, but I think my table is about as entry level as it gets.
I did take the time to flatten and cut down my 2x4s, but I don’t think it was strictly necessary. No lap joints, just screws and butt joints.
My table was inspired by @vicious1 table. 
He said it only has to be “flat-ish” enough times that I believed him.
It was half scraps, and a purchased sheet of plywood, and a purchased sheet of MDF or two to cover it.
I started with the idea that I needed a fancy table, because I wanted it to fold out the way, etc. but this “design” (I use that term loosely, because I was winging it) easily would do a full sheet if I had bought longer 2x4s for the side, and is sturdy and really all anyone needs if they have the space for it.