No matter what your warping method is, you often will need a counting string. When I first learned to make one, it was annoying to take it out when no longer needed. Jim Ahrens (A part of AVL) taught us to make this special crocheted chain that pulls out fast.
First: take a long string (maybe 3 feet for your first practices), fold it in half and slip the two tails through the loop at the fold around your first group of threads. This makes a lark’s head knot over these threads. The lark’s head is in the next photo.
With the tails of the lark’s head, you will begin to crochet around the bundles as you make them. Read on.
Measure out your next group of threads. Fold the tails between the first bundle and the new one, making a loop. Then put your right thumb and forefinger into the loop, while holding the tails with your left hand.
Encircle the new bundle with a “crochet” by using your finger and thumb to draw up another loop from the tails. Holding onto the tail, pull on the loop to snug it up around the bundle. Leave that loop and the tails dangling (don’t pull the tails through the loop, as you’ll be tempted to do).
The lark’s head is the foundation. From now on, you’ll crochet-chain using your fingers like this. Measure the next group of threads. With thumb and forefinger, reach through the old loop, drawing up a new one from the dangling tails, and tighten to secure the new group of threads.
After each crochet, both the loop and the tails should hang freely, ready for the next bundle.
This is taken from the Appendix in my book, Weaving for Beginners.