Kind of, sort of tutorial. It's more walk-through my painting process. I hope it will be useful to you.
For constructing the knotworks - as I'm still learning that, I really don't feel entitled to give advice about it. Anyway, if you're interested in this art, I can recommend you two great books - Celtic art: Method of construction by George Bain nad Celtic knotwork by his son Ian Bain. The first book has more intuitive approach, although it's not always easy to understand. The second one is more technical, yet very systematic and comprehensible.
Finished picture can be found here: [link]