I use a heated incubation box for now.
A plastic tote with rockwool insulation on the bottom and all sides; glass on the bottom and sides; one more "floor" of glass 2.5" above the first floor; all glass glued together with high temp epoxy; 15W heating cable zig zagged and held in place with electrical tape on the other side of the lower glass bottom; empty space filled with sand.
It's barbaric but when room temperature is 67-79 F, there are three zones based on proximity to the sand where test tubes can be placed for heat. 73-83; 84-88; 88-93. The last temp is if the tube is sitting on the sand - if buried, temps will increase although I'm not prepared to do that until the colony grows to a point I can move them to a vertical formicarium allowing for heat relief. I do quality control with a dummy test tube with a temperature probe in it. Its range is room temp to 130+ degrees F.
I wish there was a way to keep the temperatures more steady. The sand was the only way I could think of that could possibly mimic the natural temperature "delay" underground tunnels experience and I definitely noticed the same effect happening after I placed the sand. I had a lot of plans for this box, but will most likely switch to an entirely different setup for more control over heat. Maybe vertical walls of sand encased between glass? There needs to be some way to trap heat without the entire setup blowing up. The right mix of ventilation and controlled heat, if you will.
If you're interested in collaborating with me, send me a message. We can bounce ideas off of each other and maybe create something cool.