Front side

You should have a slip or a paper cut pattern to compare it with your crochet slip.

1) Slipknot
2) Chain stitches (width of your slip)
3) Chain 2 more stitches (this will be the first doueble crochet)
4) Yarn over, insert your hook into the 4th stitch from hook, double crochet all stitches
5) 2nd row: chain 2, turn your work, double crochet
6) 3rd row: chain 2, turn your work, double crochet
7) Cut your yarn, bind off (strain should be long enough for sewing later)

8) Put your crochet strap on your slip and set markers where to crochet the triangle (watch video how to do 6m50s) Count stitches on each side to make sure it is symmetric, if not move your markers to have the same number of stitches on each side.
9) Tie your yarn strain next to the first stitch where the first marker is located. (10m4s)
10) Insert hook into the stitch where your first marker is located. Slip stitch. Chain 1 stitch.
11) Double crochet until the second marker.
12) 2nd row: chain 2, turn your work, decrease once: 2 double crochets become one (12m1s), at the end of the row you should have 3 stitches left, decrease once, double crochet.
13) Crochet so many rows with decreases as you need (compare with your slip or pattern). I have 3 rows.

14) Chain 2, turn your work, insert hook into the 4th stitch from hook, double crochet
15) Crochet so many rows  as you need until you reach the crotch area (compare with your slip or pattern).

16) Chain 1, turn your work, yarn over, insert hook into 2nd chain from hook, half double crochet until the end of the row.
17) 2nd row: Chain 1, turn your work, yarn over, insert hook into 2nd chain from hook, half double crochet until the end of the row.
18) Crochet so many rows until you finish the front side.