I moved my sink to the corner and now water slowly collects and then drains very slowly. I thought it was the disposer, but that works fine. So, I dismantled EVERY PVC pipe to the basement and kept testing each part by adding on, letting the faucet run, and the water empty into a trash can. Each time it worked as a pipe section was added. It stopped working once I put on the last pipe in and had a closed system. BINGO - the problem is a venting one, right? So, I added an automatic air vent, but that did not solve the problem. The water still slowly collects until it backs up in the sink, then slowly drains.
Attached is a schematic. I know I have a lot of 90 deg angles to the sewer, but the AAV and continuous waste vent should handle these, right?
try pulling the rubber insert out of the top of the drain if you can. mine does that sometimes and i didn't move the sink just replaced the disposal. the rubber on top of the old one was a lot looser from age. if yours doesn't remove just use your fingers to hold it open while running the water.