Cut off the stump, using a chainsaw or a wood saw, if necessary. You need about 18 inches of stump to make a bench. If the tree stump is only 6 to 12 inches wide, cut two pieces to use as bases on either end of the bench. If the tree is larger than 12 inches, split the stump down the middle with steel splitting wedges and a sledgehammer.
Level the stump by setting it on a flat, level surface. Use your level as a straightedge and mark a line along the top edge of the stump. Cut off the section at the line, and you should have a level section of stump to use as the base for your bench.
Remove all the bark from the outside of the stump using a chisel or a flat-head screwdriver.
Heat up the wood to kill off any bugs that may continue eating the wood by placing it close to a fire. Rotate the wood to heat both sides until it reaches about 200 degrees, Fahrenheit. At this temperature all the bugs and their eggs or larvae will die.
Paint the stump surface with several layers of exterior polyurethane, using a 3-inch paintbrush. Dry between each of the layers according to the manufacturer’s directions.
Position two or three 1-by-8 planks of hardwood on top of the two pieces of finished stump. Adjust the stump pieces to sit 2 or 3 inches in from the outer edges of the planks. Step back and look at the bench to make sure you like the position of the stumps and the planks.
Drill several 2 1/2-inch pilot holes through the planks into the stump sections. Use 3-inch wood screws to anchor the planks into the tree stump sections.
Finish the bench with another two coats of exterior polyurethane and set it out to use in a scenic place of your yard.