Chris Lewis wrote:
1/2" ply isn't good enough for 16" OC, and probably not good enough for 12".
Think 5/8" or better still, 3/4".

Or tongue & groove OSB subfloor?

Charlesg wrote:
My plan is to start by snapping a line around the room showing the
height of the level floor and measuring the thickness of each strip
from there.

Use a string level to mark your corners, then snap the line (or use a
laser level as suggested by Chris Lewis)


What's the best way to cut each piece on a angle on the full
length of the piece (about 8')?

You could cut the pieces straight and use shims to make it level,
however you'll need a lot of shim material and it'll have to be placed
under every nail/fastener.

Ditto the comment about a possible need for vapor barrier. In
addition, depending on climate, what about insulating?