For the longest time,
I used a scrap piece of wood for a sanding block. It was simple and didnt
cost much. But it never worked as well as I would've liked the sandpaper
tended to shift around and tear. Recently, though, I came up with a "new" sanding
block that works really well. Not only is it sized to fit my hand perfectly; it
also holds the paper in place using plastic tubing.
To make the sanding
block, first I found a "palm-sized" scrap block and drilled a couple of rounded
channels across the top of the block. (To do this, you'll need a 1/2"-dia. Forstner
bit.) Finally, round the nose of the block on a belt sander, and if you want to
get really fancy, you can rout a finger grip on each side.