Don't replace the substrate in the tank with the laying substrate, the reccomended easiest thing to do is buy a decent sized plastic tub (I use a 70L sterilite tub) and fill it with either very damp sand, soil sand mix, coco fibre (I use Eco earth bricks) pretty well to the top but leaving 6ish inches so she has room. It will need to be damp enough to hold a tunnel as you don't want it collapsing I her. Don't put her in until she displays signs of laying, which are her belly being very full, eating less or not at all, pacing, glass dancing, and digging around the tank. I always know when my female is about to lay as she is usually a calm girl. How old is your female? You will want to make sure she gets a balanced diet with a little extra calcium then you would give your male as the eggs will drain her calcium If she isn't given extra. She should lay in about a month or 2, my female layed after 2 and then has laid 2 other clutches a month apart. She will lay subsequent clutches, they range from 10-30 eggs (my girl has laid 18, 23, and 25) without being reintroduced to the male. If you have any questions please feel free to message me, my female came to me gravid from a breeder who didn't tell me so I know all about the accidental part.