What are the dimensions of your tank?
A hexagon tank sounds cool, but it's important to make sure it is the right size for your snake.
Sand is not a good substrate choice for corn snakes. Cedar bedding is toxic to corns. Aspen is cheap, clean, and attractive.
If all else fails, you can always use paper towels.
The heat pad should be placed at one end and where the temperature on top of the substrate should measure around 84ºF. The snake should have a cooler side (somewhere in the mid 70's) where it can go if it feels too hot.