You should never crochet. It destroys your locks. All a crochet hook does is beaks your hairs into smaller and smaller pieces.
Your roots will lock. There is no secret method people with old locks use. Baby locks NEED to have between 1-3 inches of straight hair at the roots. This hair is what snags and tangles with new growth making your locks strong and roots thick. If you force them to tighten, you are going to make your locks weak and thin.
Look at my locks. If roots didn't tighten on their own, I'd have 5 inches of locked hair, and 20 inches of straight hair. If Eagles roots didn't tighten, he have 5-6 inches of locked hair and 10 feet of straight hair