How to keep flies away from curing meat
Your second suggestion is best.  When hunting, we always brought cheesecloth game bags into which to place the quarters, etc.  They worked well at keeping flies off and allowing air circulation.  I prefer the cheesecloth ones as they allow better air circulation than the muslin ones; particularly important for long term hanging and drying.  You can also just wrap the sheep in cheesecloth if you prefer.

Also, keep a close eye on the sheep.  Making pinnekjøtt and skerpikjøt as on the Faroes is partly dependent on the micro-organisms available (or unavailable) due to the salty air as well as continuous air circulation (wind).