I can’t help with Carabids specifically, but I used to dissect flea beetles many years ago as part of a research project. We used alcohol in a petri dish, a dissecting scope, and a pair of fine (tipped) forceps. Each beetle was poked where the elytra started, and basically I pulled the abdominal exoskeleton off. Males had large bright red/orange testes and were discarded. For females we picked out the ovaries and eggs, then measured the size of the eggs. I think that was done with a compound scope, but it’s been a long time ago. BTW, the reason for this was that female flea beetles seemed to stop developing eggs (except for those which were about to lay) when they were captured. The guys in charge wanted to understand why so we could rear them in the lab. Agricultural Research, on Canola.