This is a protection spell. I visualize it growing larger and larger until it spins around what I want to protect. Think "Dr. Strange." This is fairly complex magick because it is hard to remember all the details of the design. I suggest starting with a simple circle then gradually adding more elements like color, lines, other shapes, etc.
After my Celtic star is in place, I say The Rune of St. Patrick. If you've read the "Wrinkle in Time" series, you will recognize these lines as they are the chapter titles in the last book, "A Swiftly Tilting Planet."