You can google it and find instructions.

I tried

.... Some of us are aware of what you're referring to, actually.

[Edited: you posted a photo while I was typing my response!]

I'm sure you can find some instruction videos or tutorials if you dig around. But a quick search myself, I can only seem to get to links to pinterest that are the "fluff" sites with out any, actual instruction.

After reviewing a few images, it doesn't seem difficult, but will need a little work. I would suggest the following: cut into the top of a panel where it hangs onto the rod - equal widths across and same length down. Basically you're creating "fingers". You don't want to go too far down the curtain- just far enough for the number of "rows" of weaving you want to accomplish. You would probably want to sew just below the cut line across the width of the panel to prevent the cut from tearing further at any point as well.

If you want the same type of fabric, you'll need to purchase extra curtain or fabric of the same pattern to weave the fabric between the "fingers" you cut on the top of the curtain. I have seen versions done with a complimentary fabric (would suggest fabric store at that point), where fabric is just woven between the fingers.

Ideally you'd want to sew probably a 1/4 allowance or seam at any cut points ("fingers" and what you weave between them), but you could use the permanent iron on hem tape if you're less familiar with sewing or don't have a machine... or really you could just make sure the cut edges are tucked under. Just be aware that properly sewing or affixing them would prevent fraying if machine washing and drying.

I would suggest picking up an inexpensive panel or two to "test" before you go cutting expensive panels up if you're a little less experienced with DIY. I'll try to scribble out a drawing to post up to clarify my explanation here in a little bit.

My phone will only let me post one at a time: cut the top

This is is a "close up" of the fingers made by cutting. Dotted line refers to the seam you would want to sew once you get the cut length you need.

other line depicts how to weave and intertwine. You'll want to leave excess at your start point to tuck it back. Leave room at the top for the rod to be inserted

Photoninja she made me feel crazy for asking..... Thanks so much!!! You're MVP for today

Looks similar to weaving a pie crust.

I saw this on you tube and started looking for directions. Nope. No directions could be found. Thank you for asking, thank you for the commenter who tried to help with some, To the “pro” who said “no one knows what you are talking about”.

Not a Pro.

It is #35 here.

https://www.home-dzine.co.za/decor/decor-curtain-twist.html

I wish the directions mentioned how many inches wide the drapery panel should be to create the look we are seeing.

I could be wrong but the instruction on that link that says 7 panels folded in half over the rod that hang to the floor suggests to me that these are not sewn together after the weaving. So each side “panel” is made of 7 scrunched strips that hang to the floor, with the fullness providing gap coverage and the woven in horizontal strips making it hold together on top.
I remember seeing this detail in a Houzz story and thought it very pretty and unique.

i love how the “pro“ feels comfortable enough to answer for everyone. Speak for yourself. I heard the prison is hiring I think you’d be better suited working with inmates than interior design. what a joke.