How can I make a table out of a countertop?

You can get countertop special ordered in your custom size with both long ends finished in your choice of edges. The 2 cut ends would need to have a finish, either rubber cement a matching laminate endcap, (they can sometimes come off a bit easy) OR add a length of wood glued and doweled into the ends. That may add a little charm to the laminate top too. Then you just need to select what style table legs you want, as well as how high. A typical dining table is 30" high. If you're looking for a folding table, HERE IS a folding table kit. HERE IS a more contemporary design hairpin leg that would attach nicely to the underside of your laminate top.

Home Depot has a large selection of table legs to choose from. Next decision is stain or prime and paint. Either one will require a sealer. You might want to take a walk thru Good Will, second-hand shops or Habitat for Humanity for table legs.

Do you already have a piece of countertop in the above dimensions?