Got it perfectly level and no gaps!
Thank you all for your input.
I hired a pro to level the stand on my my carpeted basement floor. They used 12" x 12" vinyl flooring tiles for shims to level the stand. Once they had it level, they cut off the excess flooring material.
Day before they arrived, I traced the top of the stand on a 3mm thick yoga mat and cut out a padded "frame" for the top of the stand, and lightly siliconed this frame to the top of the stand.
This method works perfectly for me so far!