I definitely would not go cutting on those pots. They look like earthenware . . . and I wouldn't bet on your being able to notch them, without cracking them.
I followed your photo link out to your album, to see if you had other pics looking INTO the pots. You didn't, but I did learn you are probably mechanical enough to do some cut and fit testing.
There are many ways you could try this, but I'd suggest getting some heavy aluminum roof flashing, to make test "lips" with. You can get this at Lowes. While you're there, take a look at how roofing drip edges, made of galvanized steel, are formed. Keep in mind that, for a drip edge to work, the edge must slant slightly down AWAY from the direction of flow. Since you'll have to curve the formed edge, it will probably be necessary to notch the 'L' of the edge, in order to make the curve. Use silicone to attach the edge, since you'll be able to peel it off. Don't use more silicone than you absolutely need, until you're ready for a permanent attachment.
Neither aluminum nor galvanized steel will last long in that exposure, so once you have a working edge, you may want to go to an SS sheet metal shop (restaurant sheet metal) and have them make your edge in stainless. If you're using salt in your pool, get grade 316 SS or better, not 304.
I've added some Amazon links the tools you may need.
Irwin 23EL5 Vise Grip Sheet Metal Tool
Wiss M3R MetalMaster 3/4-Inch Snip
3M 08029 3M Marine Grade Silicone![]()
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