I don’t have that much flesh on my “love handles” , (at least when I’m eating right and exercising) , so I also got tired of always having red spots there. A couple of years ago I just started injecting in my butt cheeks, anywhere is fine, there’s plenty of meat there. I usually just time my bathroom visits to before or slightly after I eat and drop my pants and do it there. I use the smallest pen needle possible for my Humalog quick pens - about 1/4", so I can just stab it in. In the summer, when I have shorts on, it’s even easier, I just put a leg up on something and inject at the bottom of my butt cheek.
Sometimes I do the underside of my upper arms out of convenience. I usually will rest the arm on something so the fleshy part is loose.
I’ve been using insulin pens for 8 years now - since I was diagnosed - and have tried just about everywhere. Hope this helps.