Here’s how my husband grills salmon without it sticking to the grill:
Put several pieces of thinly sliced lemon on the non-skin side of the salmon.
Grill with the lemon side down first and flip after just 3 minutes.
Cook about 6 minutes on the skin side so it separates from the flesh. Viola.
Note: Length of cooking depends upon many factors including thickness of salmon, temperature of the grill and ambient temperature. Test at intervals.