Below is a stock image of my hot tub, a portable Voyager Spa. As you can see, although it is perfectly round (6 feet), a standard round cover won't fit because the filter is inside and protrudes out. It come with a cheap, inflatable cover, which offers terrible insulation. Long story short, I've come across a good, used round 6 foot cover for $50.
Now, I can carefully cut a small corner without too much difficulty, but then what? Tape the exposed foam? Obviously, it can't get wet. What kind of tape, if any at all? Any tips would be greatly appreciated.