Top down knitted ruffles are made by increasing the number of stitches, by 2, 3, or 4 times.
Garter Stitch Ruffle
Cast on 20.
Rows 1- 4: Knit.
Row 5: *Kfb, repeat from *. 40 stitches on needle.
Row 6: Knit.
Repeat rows 5 and 6. 80 stitches on needle.
Bottom up ruffles look very similar to the basic top down ruffles. Cast on twice, 3 times, or 4 times as many stitches as you need. Work the ruffle to the desired height. Then to decrease, k2tog (for 2 x ruffles), k3tog (for 3 x ruffles), or k2tog on 2 rows (for 4 x)
In this example, I cast on 60, then decreased to 20 by k3tog across the decrease row.