Row 18 : this row is super easy, you want to chain 3 and anchor with a single crochet (call this a wave) in the third SC from previous row, repeat until you reach the end of the row. Make sure you have 50 waves.
Row 19: chain 3 and do 3 Treble Crochet (TC) in the wave then chain 3 and anchor in the next wave after anchoring chain 3 and repeat. Tips: 3 TC will be in every other wave. Nutshell: 3 CH and anchor with a SC – 3 CH – 3 TC and anchor, repeat.
Row 20: this row is easy since we are using the half double crochet again. 2 HDC just before the trebles then 1 HDC in the space between the TC and 2 HDC after the trebles for a total of 6 HDC.
Row 21: this is the overlay row it takes a little more concentration, its difficult to explain but if you look at the photos you can understand. We are using the slip stitch SS and working in spaces and around spaces.