How to Increase Double Crochet at the Beginning of a Row
You can increase double-crochet stitches by adding a stitch at the beginning of the double-crocheted row. Increasing double crochet with this method creates a smooth, tapered edge to your piece.
Try your hand at adding 1 double crochet stitch at the beginning of a row:
Make a swatch of double crochet stitches.
Chain 3 (ch 3).
This is the same number of chains required for a double crochet turning chain.
Work your next stitch into the first stitch of the row.
This is the stitch directly below the turning chain, the one that you usually skip.
Finish the rest of the row as you normally do, working 1 double crochet stitch in each stitch across the row.
Take a look at the symbol used in pictorial crochet diagrams to represent an increase at the beginning of a row: