Choose a slab of wood for your table top. Cut it to the dimensions you desire.
Sand the slab until it is smooth. Stain the slab using multiple coats if you want a darker finish.
Apply a coat of wood sealant to the slab after the stain has dried.
Place the slab on the top of the stump and use a level to be sure it is lying flat. Use a shim, if necessary, to make the table top level.
Drill four to six pocket holes into the stump depending on the size of the stump. Use screws to attach the table top to the stump base.