such a professional outcome, you've chosen some nice lace as well! x
If anyone is having the "concave issue" here is the problem:You only want to add the three stitches on ONE end of the work. Don't make a continuous circle. Once you get to the end of the ten original stitches, flip it and work towards your stitch counter. You'll end up with one completely flat end and one curved end. I hope this comment helps! I've been crocheting here and there for a while & this frustrated me and I was quite confused at first but I kept going lol I'm glad this tutorial was comprehensive.