Start with a slip knot and chain 4. Join with a slip stitch to form a ring.
Chain 3 (counts as first double crochet) and work 2 double crochet in the ring. Chain 2 (this forms the first corner).
Work 3 double crochet in the ring and chain 2 (this forms the second corner). Repeat this two more times to make the third and fourth corners.
Join with a slip stitch to the top of the beginning chain 3. You have completed the first round of the square.
To start the second round, slip stitch in the next 2 double crochet and in the first chain-2 space. Chain 3 and work 2 double crochet in the same space. Chain 2 and work 3 double crochet in the same space (this forms the first corner of the second round).
Chain 1 and work 3 double crochet, chain 2, and 3 double crochet in the next chain-2 space (this forms the second corner of the second round). Repeat this for the remaining two corners.
Chain 1 and join with a slip stitch to the top of the beginning chain 3. You have completed the second round of the square.
To start the third round, slip stitch in the next 2 double crochet and in the first chain-2 space. Chain 3 and work 2 double crochet
in the same space. Chain 2 and work 3 double crochet in the same space (this forms the first corner of the third round).
Chain 1 and work 3 double crochet in the next chain-1 space. Chain 1 and work 3 double crochet, chain 2, and 3 double crochet in the next chain-2 space (this forms the second corner of the third round). Repeat this for the remaining two corners.
Chain 1 and work 3 double crochet in the last chain-1 space. Chain 1 and join with a slip stitch to the top of the beginning chain 3. You have completed the third round of the square.
You can continue to make more rounds in the same way, increasing the number of chain-1 spaces and 3-double crochet groups on each side of the square. You can also change the color of the yarn at the beginning of each round to create a colorful pattern.
To make a blanket, you will need to make as many squares as you want and join them together. You can use a whip stitch, a slip stitch, or a single crochet stitch to join the squares. You can also add a border to the blanket by working one or more rounds of single crochet or double crochet around the edge of the joined squares.