I'm not on the carnivore diet but I eat very low carb and dose for protein. I dose at 1:15 (50% of what I dose for carbs) with regular insulin (ActRapid), and use split bolus taking 2-3 injections per meal. For the carbs (15-20g) I pre-bolus by 20-30 minutes, then eat and dose for the protein after the meal.
How many shots I take depends on how much protein I eat. If it's less than 30g it's a single shot, and if it's more I split it in two to avoid hypos. Most of the time I inject for the third time an hour after eating. It depends on the fat content of the meal though. Pork belly and sausages are slow to digest, so it happens that I take the second protein dose several hours after eating.
I use the libre and scan a lot after meals to time the dose. Sometimes I mess it up, but for many meals I flatline and my last HbA1c was 32, so this way of eating works.
If you haven't read Bernstein's Diabetes Solution, it's a good starting point for insulin and protein. Then there's some trial and error. In the beginning I used to take the whole dose before eating and go hypo so I started splitting it. The exception is breakfast where I eat no carbs and take one shot. If you eat the same things a lot it gets easier with time.