There's no rule of thumb where to slice when propagating "pepper" cuttings.
No joke, I look for the stems that are or about to flower. I was making "Pico de Gallo" for Superbowl last year from fresh "Caribbean Reds" out of my grow room. The plant was from a clone taking in November. I sliced from the green, (never the woody part of the stem). I used rockwool with a cloning gel....works great! I have used rooting powder in the past.. and will in the future if I run out of gel. The key is to dampen the stem prior to dipping it into the powder, and also make a hole into the soil, perlite, or vermiculite ahead of time if using those mediums. I'll then set the cutting into the hole and carefully pack the medium around it. Some people try to slide the stem into the medium and all the powder comes off......
When using rockwool, I prepare the cube with a ph conditioner the day before. Once planted I place the cubes in a flat with a tall dome. A clear litre size plastic bottle cut in half-ish would work for individual cubes. The key is to keep the cuttings out of strong light for a few days. Also its very important to keep the leaves hydrated. Rooting usually takes place within 2/3 wks with the optimum conditions.
I didn't fuss with pepper clones this year but shifted over more to the over-wintering.
However I've cloned about 40 "Martha Washington" Geraniums....using rooting power into soil.
But that's a story for the "other" growing forum...
Good luck with the cloning
My info is how and why I do things..........it may however, not acomadate everyone............
Greg