I don't bother securing anything to the floor; I just make clamp blocks out of plywood (glued together to achieve at least 1" thickness) or dimensional lumber.
Just cut out a bit less than a half circle on each piece and screw together. I'll also put a bit of construction adhesive where the blocks contact the post to ensure they won't move...
Here is a quick sketch I slapped together, as pictures are worth a lot of words around here!
The actual number of blocks would really depend on what you are using to cover up the post (and the height of course).. Some 3/4" plywood would probably only need 2 or 3 blocks.