I figure out this method by myself.
Crochet round without a seam. I want to show you haw I make so perfect round. I use this way for different patterns. This method is applied for the bottom and for the sides of the basket. The video has Russian narrator, but I hope it is clear
My instargram / nadezhda_lab
My shop https://www.etsy.com/shop/NadezhdaLab
The scheme of the circle https://goo.gl/CUQRf7