Add Miter Binding Corners On Blanket

Has anyone tried to add border to Blanket, Quilt, etc the way this lady does it.

Video 20: Sewing on Continuous Binding with Mitered Corners

Seems she doubles the border, with the open fold on same side as blanket edge. After creating the corners, she folds it over to the other side of the blanket.

I already got the border, https://www.amazon.com/gp/product/B000AXRW76/ref=ppx_yo_dt_b_asin_title_o05_s01

but I thought I had to open the fold and then insert the blanket edge.


Any ideas?