Males usually are not very large when fully grown, and you can keep one in a 10gal, but a bit larger is always better for an adult. 10 gals do not give alot of space for temperature gradients in my opinion when the occupant is of size to fill up a good part of the cage.
Baby sand boas are easy pickin's for predators if exposed. That is why they do so well in small plastic shoebox cages when small - they feel secure. They also feel secure with the weight of substrate on top of them. They feed like mad when they have that going on. He will be OK in the 10 gal if you want. I would cover 80-90% of the screen top with plastic or styrene foam. Full screen tops are great for lizards but are not ideal for snakes that spend most of the time in the ground. I would put a water dish large enough to maintain a moderate humidity in there. Impossible with a full screen top. If your ambient humidity is already moderate, you can ignore. Remember, heat pads dry out animals when moisture is allowed to escape freely thru the cage top.
If you want to try hides, make them low. I made some out of 1/2 inch styrene foam. The walls are only 1/2 inch high made by cutting the foam in thin strips. I glued them onto the top piece with a glue gun and painted the hide black inside and out.
With sand boas, you can probably just lay a piece of cardboard or foam flat onto the substrate. Wrinkled up packing paper works really well on top of the substrate. My adult sandboa will sit under that paper on top of the substrate with her nose peeking out waiting to attack. Obviously she feels secure with the weight of the paper on her.
I understand that you probably want a display cage. Otherwise I would suggest a plastic storage box that measures more or less in the area of 22 inches x 14 inches for an adult. A 20 gal long would be nice for an adult or two.
Sand boas are IMO the best boid snake to keep in terms of ease of care.
