Never done slin, but do Human Chorionic Gonadotropin (HCG) every weekend. Basically, you pinch the skin where you plan to inject and go for it. My doc always told me that the goal of sub Q injections was to get the meds into the rich capillary bed, just below the skin. For me, that ends up being just about half way down the insulin needle. You may end up with a small whelp but my doc says that is how you know you hit it about right…not too deep or too shallow. The whelp dissipates before too long. Hope this helps.