These look similar to the shoe patterns from Make and Do Crew. Here are two of the patterns; there are links to others on these pages.
https://makeanddocrew.com/seaside-crochet-shoes-rubber-bottoms/
https://makeanddocrew.com/free-crochet-slippers-pattern-flip-flops-sole/
I made the second one with crochet cotton, and found that they stretched a lot. I like the suggestion to trim the heel in the OP link; that might help keep the shoes on my feet!
I tried them without the plugs, and found that they created little suction cups on laminate flooring. So I put the plugs back in, but have found that I can still feel the cut edge on the plugs, even after re-trimming a few times (I guess I don't have the right tools to trim them short enough).
I haven't decided whether I will try again, so I appreciate this link!
-- Cheri