Three ways off the top of my head to use crocheting:
1) Any knot spell goes well with crocheting. Say a charm for each stitch/loop and when you tie off the last bit say a bit of an ending phrase. This can be extremely meditative. One of the most ancient roots of magic is spinning and weaving, and crocheting is weaving. Spinning and weaving both are very effective at bringing one into a trance state, which is a great place to launch off to your astral temple.
2) A sacrifice/offering. Create your crocheted object and then either offering it to the spirits you are working with, or give it to a person in serious need, a homeless person or a charity for those in serious need. The gods often masquerade as the needy, and giving offerings directly to the needy is one of the top ways to please them. (Macha as a poor pregnant momma, Zeus as a poor old man advising Pericles, Llew and Math ap Mathony posing as craftsman, Pallas Athena posing as old Mentor and the list goes on!) Alternatively to giving the corcheted object to a needy person, you can throw it in a fire or bury it if you use biodegradable yarn (read cotton).
3) OR you can even make an altar cloth for your undercover altar.