There are a lot of different ways to make a hot box to warm your oil based clay. Tuck Langland has a very nice one that he makes from an old fridge. But you can also go very low tech, as I did here. I simply went to the dollar store and purchased a styrofoam cooler for $1. I also got 3 aluminum disposable pans for $1.
I turned the cooler on its side and traced around the dome of a cheap shop light. Next I cut out the circle I traced using a sharp knife - being sure to cut 1/2" INSIDE the circle. I placed a 40watt bulb in the lamp and place it on top of the cooler. Since the circle that I cut out is a bit smaller than the lap - I sits just on top of the cooler.
Finally I took some cold, hard chunks of jmac classic clay and tossed them into one of the pans and slid it into the cooler and closed the door (which is really the top of the cooler). Within 10-15 minutes I have warmed clay.
This isn't perfect - it's kind of small and the center chunks of clay get melted while the outer chunks warm less - but for $2 and a lamp I already had, it sure beat sore hands from trying to use cold, hard clay or burned hands from lava-melted clay.
Yes - I know that the old, hot lightbulbs may be be a thing of the past and hard to find soon - but I imagine that I can get creative and find another heat source in the future - for now, this is great for smaller budgets, smaller space and smaller amount of working clay fast.