After the sanding dust has settled, set your hunk of tree upside down on a soft surface like a table covered with a blanket.
Arrange the hairpin legs in your desired stable orientation. I chose to use only three legs because I knew it would be challenging to eliminate wobble due to the more uneven underside surface of the wood. A tripod never wobbles!
I was not concerned with making the table perfectly level-- if you are, you'll have to plane and/or sand the underside first to make it flat!
Mark the position of the mounting holes with a pencil.
Drill holes to match the recommended pilot size of your screws. You can use a piece of tape on the drill bit to limit the depth of each hole (and helps prevent you from accidentally drilling all the way through).