Here’s what I did. One sheet of cheap plywood, ripped down the middle into two sheets 2’X8’. Mine is 3/8” thick, with a 6’ stiffener screwed, centered, along the bottom. The stiffeners are two, 6’ pieces of wooden banister. They have one side flattened, and are thick and strong.
I use 4ea wooden strips, 2” wide, 1” thick, and about 12” long as connectors. As I recall, they had been used in the garden, at ends of rows, with seed envelopes stuck on them, in a previous life. Don’t use wood screws. Use little machine screws with countersunk heads. Use them as little bolts, with washers and nuts on the underside of the plywood. Countersunk heads in from the topside, so your work surface is smooth.
When I wanted a large work surface, I connected the two pieces along their 8’ side, using all 4 slats underneath. When I wanted a long, narrow surface, I connected them at the 2’ ends.
Use 6-8 saw horses underneath as support. They have to be all the same height. At first, I tried to make my own sawhorses with 2X4s, and those steel attachment jaws. Never worked worth a tinkers’s dam. I bought the folding ones, and never looked back.
Other builders have different approaches that work well too.