I setup the saw so the table is flat to about .020 inch (along with the arms). The sled I made was an idea from a Utube vid. He adjusted his sled to the wood. I adjust the wood to my sled using a shim here or there. I used a 1 1/2" straight bit to do the routing and as long as I don't push down and only across, I get very minimal bit marks and those sand out very very quickly. I did a full 30" by 72" edge glued slab and after it was done it was flat flat (laying a 6 foot staight edge on it to check) and it took about 30 min including sanding.
"If the tool's not right, the man's not bright"