as Dawg said foam board is easy to work with, corners can be taped.
Consider having a temperature controller for the heat, Christmas brought an ink bird (rated at 220 volt) which would allow setting a narrow temperature band. At work I use controllers with a PID tuning program and solid state relays that can cycle on/off every second and can stay within 0.1 C. ,,, An undersized heater which runs 75% of the time will be more consistent (ex a flat heating pad) than a large space heater cycling on/off four times an hour.
If you want cooling mechanical refrigeration requires cycle time for the pump. A thermoelectric (ex twelve volt car beverage cooler/heater) will allow you to cycle quickly ,,,, and could have polarity reversed to act as a heater.
Good luck on the project, Omega engineering is my favorite place for build your own pilot plant parts and their how to section in the back of the catalogue has good info on how parts work.