A trick my dad taught me. It was originally for doors, but I've
applied it to other things.
If you're not finishing the edges (or if they'll be hidden anyway),
you can use them to support the board. How? Pre-drill a hole on
those edges near each corner. Find a long wood screw that's 100%
threaded. Cut a small scrap of wood, drill a hole through it, and
screw it onto the screw all the way. Now screw the screw into your
board "just enough". Now you have four "legs" attached to your board
in places where it won't show; you can use these legs to manipulate
the board (i.e. flip it over) while finishing it, and to suspend the
board while the finish dries. If the scraps happen to be round, you
don't have to worry about them tipping over either.
For larger pieces, I put screw-eyes into hidden edges, and suspend
them from my shop ceiling. Then I can stand on both sides to finish
it. The largest I've done this way was two 100 lb table top halves.
They were hung from I-beams via 3/8" threaded rod.