How to create a DAO?

I have seen some online guides about using DAO building services but I didn’t particularly like those DAO building apps and I’d rather build one from scratch, via programming.

How do I create a DAO?

The main idea is that there will be some minimum buy-in, like 50 Euros, and then members can vote on decisions for the group. The decisions would automatically trigger payments from the DAO’s funds or they could be unenforceable, i.e. actions for the group which it would be assumed people would abide by. Also, the DAO would have the ability to close itself off - the members can vote whether or not to accept new members during various times.

So what are the fundamentals of building something like this? Do you start by writing a smart contract explaining the terms of the DAO or something?

Thanks very much