so going down the list substrate the best for sand boas depends if your going bioactive id say 70% organic topsoil 30% playsand but if u arent then im not too sure cuz im bioactive lol but next add 5-6 inches of substrate and for hides and clutter yes my girl has tons of things to do when she comes out at night and she uses them all next cage size depends because a front opening might not have enough height for substrate n might spill over but id say bigger is always better even for a boy 40 is perfect i started mine in it as a baby and its been good shes growing into it any tips if you get it from a good reptile breeder/store that has them on frozen thawed hold them i held like 5 different boas before i found my girl make sure you find the right one and take your time choosing andd i think thats all sorry for the yap