Chain 58 + 2 (to turn around).
1. (RS) Crochet 1 hdc into third chain from the hook. Crochet 1 hdc into each chain = 58 stitches. So ch 2 in the beginning of the row is not counted as one hdc. The rug should always have 58 stitches. Chain 2 and turn the work.
2.-3. Crochet 1 hdc into each stitch and end the row with ch 2 and turn the work = 3 rows with the background colour. Here you can of course choose to crochet less or more rows with the bg colour. I tend to crochet 2-5 rows with the bg colour before beginning the pattern. During these rows you can also carry another yarn inside the stitches so that the whole rug has same thickness.
4. (WS) Time to join in a new colour and start crocheting the pattern according the chart. Crochet 5 hdc with the bg colour, and when crocheting the 6th hdc, make the last yarn over with the motif colour. Lift the yarn of the bg colour to the wrong side of the work before taking the motif colour on the hook. Do this always on the wrong side. I also have the habit of pulling the background colour tight at this point because it tends to be a bit loose. Crochet 1 hdc with motif colour, but make the last yarn over with the bg colour (picture 1 below). Crochet 1 hdc with the bg colour without carrying the motif colour inside the stitch, but pick it up after that (picture 2 below). Crochet altogether 8 hdc with the bg colour, and the 9th is crocheted with the motif colour again (picture 3 below). Pull the yarn of the motif colour gently before crocheting the 9th stitch with it, so that the yarn travelling inside the bg colour is tight enough. Repeat 6 times (as there are 6 diamonds in a row). Leave the motif colour here, to the last diamond, pull the yarn tight, and crochet rest of the row with only bg colour (picture 4 below).
5. (RS) Crochet 5 hdc with the bg colour and then 2 hdc with the motif colour (picture 5 and 6 below), and then 7 hdc with the bg colour according the chart. Remember to carry the bg color inside the motif colour during both stitches as always when crocheting the right side (picture 6 shows how your rug should look like at this point on the wrong side and you see the beige background yarn travelling inside both stitches made with lilac motif color).
6. (WS) Crochet 5 hdc with bg colour, 3 hdc with the motif colour and 6 hdc with the bg colour. When crocheting the first stitch with the motif colour, remember to lift the yarn of the bg colour to the wrong side (picture 7 below), then crochet the first stitch without carrying the yarn inside the motif colour (picture 8 below). Continue according the chart during rest of the row (6 stitches with the bg colour, 3 with the motif colour and 5 with the bg colour at the end of the row).
As you probably notice by now, you always widen the diamond pattern on the right side of the motif/diamond with one stitch during each row.
7.-11. Continue widening the diamond with one stitch each row.
12. (WS) Now the diamonds have reached their widest point, 9 stitches. Almost the whole row is crocheted with motif colour, except the two hdc in the beginning of the row and at the end of the row. I tend to call this row “the easy row” because I don’t have to constantly be changing colour :-).
13. (RS). During this row you start to decrease the width of the diamond motif to 8 stitches. It is made in the same way as widening the motif, one stitch each row. Crochet the first hdc with the motif colour into the same stitch which was made with the motif colour during the row 15. The actual decreasing is made on the left side of the motif.
14.-20. Crochet as before, decrease the width of the diamonds 1 hdc each row.
21. (RS) The first row of diamonds is now finished. Crochet the whole row with the bg colour. After this row you can either continue with the same motif colour or change it. Whenever continuing the next row of diamonds with the same motif colour, I tend to let the yarn of the motif colour to travel inside the stitches during the row to the point where I start the next row of diamonds. If I do change the motif colour, I still tend to carry the yarn of the motif colour inside the stitches to the same point then just cut the yarn and start with the new colour during the following row. This way the thickness and probably width of the rug too remains the same and at the same time the tails get weaved in.
22. (WS) Start the same way as with the first row of diamonds (row 4).
And continue crocheting as many diamond rows to your rug as you wish. I've made 4-5 rows to my rugs so far. Enjoy your work every now and then and rest and stretch. When I keep a pause, I also have the habit of putting the unfinished rug on the floor, admire it from different angles (because it looks different) and enjoy a cup of coffee or tea (and maybe some chocolate) - and just be happy about what I am making and achieving.