How to make a bottomless/open bottom/upskirt skirt?

[Temp229482]

I'm a beginner to blender and so far the only thing I've been able to do is shorten a mesh. Does anyone have a tutorial on how to make a skirt bottomless? I want to do something like this: https://juliejsimsstuffadult.wordpress.com/2018/03/22/sims-4-female-pleated-upskirt-by-julie-j/, but with a different skirt. Is it possible to shorten a mesh and then make it open bottom? I've looked at tutorials about making a transparent skirt but I don't have enough experience to follow those directions and then know where to stop before changing the texture (I don't want something see-through, just open bottom).

 

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