Merry meet. There are lots of ways to make a bos. On eBay for very reasonable price you can buy hand carved wood bos's that enable you to add and take out pages you can also buy bound books that are blank to write in that you can't add or remove. Myself as of now I am using a black binder with page protecters and write on parchment for the spells. Its all personal choice
A book of shadows is yours you can do what ever you want with it there is no wrong you right way to make one. you could buy one but if you make your own from scratch you put more of your own energy into it making it better but it doesn't really matter.
Mine is an abused spiral notebook as it is ever changing. Someday i will make a nice one to pass along just like publishing a book. Although that may be a mute point now with the internet. Theres been times where i didnt even have a notebook. Just scraps of paper and my phone with the internet and this sitd when i was working for the carnival, traveling light and liveing in a bunkhousde.