Looking through some references it appears the G1000 only depicts holds on published IAPs, and my advice would apply only to the G3000. Sorry about that. G3000 allows holding anywhere on request and I think my method would work on that machine. The only other method would be some sort of waypoint assortment as others describe. Since that method is certainly not convenient, I do not think there is any way to do this on the G1000 with AP engaged. You might treat it as a DME arc around a user waypoint and hand fly it though. That's easy enough with the virtual HSI it has.