This is a pretty basic pattern.
I wanted something I could adapt pretty easily.
All hand towels are not the same width and I didn't want to get caught up in trying to have an exact amount of stitches for the first row.

The towels I've used are usually about 16" or 17" wide.

I have always used cotton worsted weight yarn - mostly Sugar 'n Cream.
I like how it holds up and I sometimes make a matching potholder.

I use an H hook

I cut the towel in half and sew a 1/4" inch hem across the cut edge to help prevent raveling.
Using the yarn I'm going to use for the topper,
I then do a blanket edging across the hemmed edge.

How to do a Blanket Stitch Edging

This is how my edge looks.

Stitches used:  Ch = chain; sc = single crochet; dc = double crochet; dc dec = double crochet decrease; sl st = slip stitch

To do the topper .....

Row 1:  Put the first loop on your hook as if you were going to do a chain then, with the right side of the towel facing you,
insert the hook in the first loop formed by the blanket stitch.  Work a single crochet in that loop and all the remaining loops.  
I have had as few as 47 stitches and and as many as 58.  It all depends on the width of your towel and the spacing of your blanket stitches.
Ch 2 and turn you work.

Row 2:  Double crochet this row, but decrease the stitches to 28.  For example:  If you have 56 sc, you just do a dc decrease (double crochet
2 stitches together) across the row; if you have 48 sc you will need to do 20 decreases.  Space the decreases as evenly as possible, but
don't get too worried about it because the top ends up being gathered and will look fine.  Turn.     (28 dc)

Row 3:  Ch 1, sc in each stitch, turn.     (28 sc)

Row 4:  Ch 2, Dc decrease across, turn.     (14 dc)

Row 5:  Ch 1, sc in each stitch, turn.     (14 sc)

Row 6:  Ch 2, (counts as first dc), dc decrease in next 12 sc, dc in last sc, turn.     (8 dc)

Row 7:  Ch 1, sc in each dc, turn     (8sc)

Row 8:  Ch 2, dc in each sc, turn     (8 dc)

Row 9 thru 16:  Repeat rows 7 and 8.

Row 17:  Ch 1, sc in each dc, turn.     (8 sc)

Row 18 and 19:  Ch 1, sc in each dc, turn.  (8 sc)

Row 20:  (do not chain) sl st in first sc, skip next 2 sc, 4 dc in nect sc, 4 dc in next sc, skip next 2 sc, sl st in last sc. Fasten off.