I've only done one patch. Well, DH did it, 3 years ago. He used a bicycle inner tube patch kit. I don't reccommend it of course, I'm sure stuff that's actually MADE for ponds would be much better! But, in three years it's never leaked so I think you'd do fine with the standard patching kits.

Tenroc, the patches work great and are stronger than the original liner, once applied.
Before applying the EPDM patch, clean the area where it is going thouroughly and wipe it off with cleaning solvent. [gasoline will do the job] then wipe it dry.
You can if you wish, you can apply a coating of rubber adhesive, the type used for bicycle inner tube repairs, to the patch area before applying the EPDM patch. Let the adhesive dry. That dry adhesive coating will help the patch's adhesive stick to the liner even more.
Be sure everything is flat, dry and there are no air bubbles under the patch. If you can use a small roller to press the patch down as you apply it, so much the better.
The EPDM patches usually come 12" X 12" size, [adhesive already on one side] but you can buy the one-sided splicing tape, which is 6" wide, by the linear foot. The tape might be better for your situation, as you do not need to cover a foot square area to patch a 2" slit.
"Horton"

I just found a small hole in my 45 mil EDPM liner. It's about the size of the tip of my little finger, and it's just below the water line, about 5 inches from the liner edge. I bought a Sunterra PVC Liner Repair Kit at Menard's before checking this forum. Does anyone know if this kit will work okay? It includes 2 4x6 patches and a tube of adhesive. The patches have a dull satiny finish on one side and glossy on the other. I assume the dull side goes against the liner, but the instructions don't say anything about which side to use. Does anyone know, or wish to offer an opinion?

indiancreeker, my opinion is that I would not use a PVC repair kit on an EDPM liner. They are 2 different types of materials. PVC plastic is not the same as EDPM rubber.

When I first built my pond (4 years ago) I had cut a 1 1/2 inch circular hole in my liner for a pipe boot. That hole turned out to be unusable because the contractor who laid a concrete ring around the perimiter of the pond had clogged the pipe.

Anyway, I read somewhere how to patch a small hole using a scrap of EDPM and PVC cement (believe it or not). I cut two 2 inch EDPM circles and glued them over the hole, front and back, with the PVC cement. The patches stuck to each other and overlapped the hole. No leaks for 4 years now!

Bottom line: for relatively small holes you don't need to buy expensive patching products. A scrap of EDPM and some PVC cement (leftovers from the initial install and therefore FREE) will work just fine.

If you want added peace of mind, you could run a bead of silicone sealant (also left over) around the edge of the patch after the PVC cement dries. That's not necessary, but if you tend to worry about things, it would help your nerves.