I cannot believe how many crochet designers (and craft pattern makers in general) are afraid to tackle e-books. I call e-books my residual income. Make it once and it pays you over and over and over. Once you upload an e-book you really never have to think about it again except to check your earnings.
I sell way more crochet patterns on Amazon and B&N than I could ever sell on Craftsy, Ravelry or Etsy.
Because most crochet/craft patterns are only a few digital pages they are much easier to format than say a book. Even I can format my own crochet patterns. As I have said before BE SURE you type them in Word 2007. This will make you life much easier!! Then just upload the file to Amazon, fill in your price points, upload your cover and you are done. Be sure to open the preview and make sure it formats correctly. If your pattern has a ton of pictures this may be harder. In that case I pay someone to format mine for me.
The great thing is once you get selling and adding more patterns; Amazon will bring your pattern up as "recently bought" which is a huge bonus!! I have even had Amazon put my patterns in several of their emails. I have to tell you I love love my monthly checks from Amazon.com and B&N.
As usualy SEO is going to play a big part in how many crochet/craft pattern e-books you sell. Make sure your title is full of your best keywords!!! This is how people will find your pattern.
A good cover is a must too! Be sure you make the cover the size Amazon recommends.