The weight yarn and size needles you use will determine how this turns out. Baby yarn (Fine:3) on a US 8 or 9 needle knit to about a 3-foot diagonal measurement will be a light and lacy baby blanket. Bulky yarn (Bulky:5) on a US size 10 or 13 to a 4- or 5-foot diagonal will be a thick and heavy afghan/throw. Cotton worsted on a US 5 or 6 to an 8- or 10-inch diagonal will make a nice washcloth. You will have to calculate the amount of yarn you will need from a gauge swatch made from similar weight yarn.
Cast on 3 stitches
Row 1: K1, kfb, k1
Row 2: Knit. (4 stitches)
Row 3: K1, k2fb, k1
Row 4: Knit (6 stitches)
Row 5: K3, yo, k3
Row 6: Knit (7 stitches)
Row 7: k3, yo, k1, yo, k3
Row 8: Knit (9 stitches)
Row 9: K3, p1, k1, p1, k3
Row 10: K3, yo, knit until 3 stitches left on the row, yo, k3
Row 11: K3, *p1, k1, repeat from * until 4 stitches left on row, p1, k3
Repeat rows 10 and 11 until you reach the diagonal width you desire. After you have finished an odd numbered row, begin decrease:
Row 12: K2, k2tog, yo, k2tog, knit until 6 stitches left on the row, k2tog, yo, k2tog, k2
Row 13: K3, *p1, k1, repeat from * until 4 stitches left on row, p1, k3
Repeat rows 12 and 13 until 9 stitches left on row.
Row 14: K2, k2tog, k3tog, k2tog, k2. (7 stitches)
Row 15: k2, k2tog, k1, k2tog, k2 (6 stitches)
Row 16: K1, k2tog, k2tog, k1
Row 17: k2tog, k2tog.
Row 18: K2tog.
Bind off and weave in ends.