There are two problems for everyone wanting to put their scope in a non-factory box:
1, humidity/damp control, which is a problem for everyone and can ruin scopes if appropriate precautions are not taken.
2, suitable support, which we can design for
No. 1, A good step in controlling damp is using a desiccant. You can spend a fortune on Branded products, or save a fortune and make your own as Wavy suggested. I've made desiccant 2" plugs for my scopes and little sacks from old socks. When they change colour indicating they are saturated, you bake the desiccant in the oven following the desiccant supplier's instructions. Be aware that the desiccant needs regular monitoring and recharging. I have a routine of checking every month, and I need to recharge them every month. Don't check and recharge, and you may as well not have them.
WHERE you keep your scope is also just as important. I've seen stonking good Maksutov ruined because even though it was kept in its factory made case, it was kept in a garage with poor ventilation. The stink of mould was quite a smack in the nose when the case was opened
Only place for that scope is the tip now
No. 2, I've also made a few scope cases. Designing a box needs you to think about how you expect to store and use the scope. If you go camping the case needs to be robust to take the knocks and be able to deal with having stuff loaded on top of it. You cannot drive safely if in the back of your mind you are constant worried about the fragile scope in its eggshell case. But if you keep it at home, you can then give a little more preference to the case's appearance.
Below are two cases I've made. One is for a fork mounted 8" SCT, the other for a 9" Mak. Each case snuggly holds each scope in place, appropriately supports the OTA (each scope has different requirements according to how they are configured), and because they are kept at home I've made certain aesthetic choices, but they are also robust enough to have stuff chucked on top of them.