Based on the diameter of the anchor, select an appropriate length of webbing, wrap the webbing around the anchor 3 times, and tie an overhand follow through bend with its ends. Dress the wraps in a way that will position the bend on the first wrap and next to the anchor, pull the remaining two wraps and attach a steel carabiner (with the gate pointing down hill from the anchor). Attach the next link of the system to this carabiner, i.e. anchor plate, figure 8 on a bight, systems rack or tandem prusik belay.
Rope may be used in place of webbing when wrapping very large anchors, i.e. a boulder ten feet in diameter.