Donna, I do the same thing you do! Free, sturdy pots that take waste right OUT of the landfill!

Since the pot MIGHT sit on a flat non-porous surface if I give it away to someone, I usually make some of the holes extend over to the side, and melt them a few mm up the side of the plastic. Or I just poke an extra "air hole" or two low down on the side of the pot.

I imagine that "venting" it might be good for the plant, if all the holes on the bottom were squished flat against something that won't let air in or water out. But I might just be looking for more ways to fiddle around!

It works with quart yogurt tubs as well as pint.
And 20 ounce soda bottles (3" pot).
And 2 liter soda bottles (TALL 4.25" pot).

I only use straight-side soda bottles, because pushing a root ball out of a wasp-waisted bottle wouldn't work easily (but I could cut the bottle away if I really wanted to push it. But I wouldn't give a seedling away like that.