That's one way.
Another is simply to choose two a/d that straddle your bimbling area as your departure and arrival a/d. By default you'll get NOTAM for 10nm either side of the direct track between them. Effectively you've defined a box. Adjust the "narrow route width" to enlarge the box if necessary. To ensure you get a/d NOTAM include any other a/d you might use as alternates.
The route will automatically be saved in the "Briefing Handbook" and can be pulled out and re-used whenever you want.
I use one from Sandown to Kemble to cover my bimbling area from Popham.
Mike