For this Doll Blanket I used:
Size J crochet hook (6.00mm)
Leftover yarn (I made sure to use the same thickness yarn for the entire blanket)
The first thing I did was make a big yarn ball of my scraps, using a magic knot to join the different colors. Here is what I did next:
Chain 51 sts
Double Crochet in second chain and in each chain across. Chain 2, turn (50 sts)
Double Crochet in second stitch and in each chain across. Chain 2, turn. (50 sts)
Repeat this row until the blanket is a size you are happy with. (I Double Crocheted 30 rows)
You could make a much bigger scrap yarn blanket and easily clear out your entire scrap yarn pile!