Making a closure is quite easy. There are a few different ways to make closures. Here are some free youtube videos to assist you. Please understand that to make wigs or closures for a customer you need to have public liability insurance before you commence trading and a relevant certificate for the method you are undertaking.
https://www.youtube.com/watch?v=O83hWc4Okdo&t=12s
https://www.youtube.com/watch?v=w4CA1pAYTBI