quad injections are the easiest ever...
ventroglutes are easy too once you get the spot down
lats are weird at first but go well with low amounts (2-3ml)
wait at least a week to hit a spot again if you want to minimize scar tissue... use as low concentrations as possible (more volume is much more comfy than higher concentration, believe it or not). use as small needles as possible (insulin pins for true trt (small volume), 27G for bigger shots)
I don't think 2-3mls is really small for lats. I'm a fucking bat with enormous lats, but it's not about the size. That shit feels like a ball of tough connective tissue, and I'm the type to actually stretch and foam roll lots. I'd personally recommend no more than a ml, but then again, what's the point if it's just a ml? Unless it's TRT which is another story.
If OP is talking strictly TRT, get some slin pins and try subq. I wrote it off because of a few bad shots, but if you get the swing of things it actually works well. It's very good for TRT and I spent nearly a year doing that.
Otherwise, quads and glutes like jizmo said. These muscles should be able to hold enough of whatever you're pinning. If it doesn't, then something doesn't add up and you need to reevaluate what you're doing lol