Mayfield White Hills
The White Hills in Mayfield (near Gunnison Utah) are fantastic for hill climbing. The hills spread out for several square miles and provide more challenging hills than you can climb in a weekend. It's like a smaller closer Caineville. The terrain which is mostly dirt and shale surprisingly has a lot of traction even when it's dry. There are plenty of razor back trail right on top of the hills connecting most of them.
I almost forgot about this place. It's not that far away and there are so many hills to climb. It's easy to get creative with so many line choices. Not much vegetation grows on these hills so making your own line isn't even an problem.
From Gunnison head East on 600 South for about 4.5 miles. You'll cross a canal and turn right. Find a place to park on the East side of the road anywhere for the next mile.