A "floured board" refers to a flat surface, like a cutting board or countertop, that has been sprinkled with flour. This is often done when baking or cooking to prevent dough or other sticky substances from sticking to the surface. Full definition
Once the dough is ready for rolling, put it on a well floured board, dust the top with flour and roll it out with a floured rolling pin. (justalittlebitofbacon.com)
Take dough out of bowl, if used one during rising, and place on lightly floured board. (redstaryeast.com)