When I first tried the stationary boundary on my Oculus Quest 2, I was incredibly annoyed because it was way too small. Any slight movement I made caused the guardian to appear and killed immersion. If I turned off tracking, it made most of my apps unusable. Worse, there was no way to make the stationary boundary any bigger (at least as of this writing in October 2021).
However, there is an easy fix to this. Simply switch to a roomscale boundary and draw a big circle around yourself.
I didn’t think this would work initially because my couch was against a wall. But, the roomscale boundary can actually be drawn right through walls and other objects. At least far enough through walls that the guardian won’t constantly be popping up and annoying you.
Just remember to stay on your couch when taking this approach. Don’t stand up and try to walk through your wall.