I think the issue you may be facing is just the difference between crochet and lace patterns. Lace generally consists of motifs (the fan) and lacing (the pyramid of spaces), and unless the pattern is for a specific use (like a clothing insert or border) the lacing part won’t be included in the pattern.
The good news is that lacing is just connected chain stitches.
I’m still looking, but at the very least I know I can find a pattern that includes the pyramid lacing to join up with the big shell stitch.
I think I figured it out it’s Tunisian crochet, TLY yarn crafts has a version of this but it’s not the same this one has a second layer for the fan I’m working on something tonight but I think I can replicate this! Let me try and do a swatch for you in a few hours and I’ll post a picture. If I can’t figure it out I will let you know.
Okay I changed my mind it’s not Tunisian and I think I know how to do it I just need to figure out the multiples to chain for the foundation give me a few hours I might have it
I downloaded the image on my iPad and am working off of it to start it, it’s not the same but similar this one has three row of double crochets instead of two.