Oh, that's a sore spot with me, but I'm glad you asked!
So, for the purpose of full disclosure, I have a personal and professional grudge with PyPA, which also touches on how pip is being managed, beside other packaging issues. It's not the side you want to be on, so, be warned!
So, without further ado: I write my own code to generate the deployed artifact. In my case, I take all the wheels installed in my environment, extract them, and merge them into a single wheel. The process also usually involves removing a bunch of junk from the packages packaged in such a way. You'd be surprised how much nonsense people put in their distributed packages... like, their unit tests, or documentation in HTML / PDF format, __pycache__ files (together with the sources)... the list goes on.
But, it works because I curate what's being installed. I don't trust pip to install just or everything I need. I run it in a separate environment, where I examine the packages that have been installed as dependencies, figure out why any of these packages were installed (you'd be surprised how often you don't need them!), then, I make a list of the dependencies I actually need, with the exact versions and checksums, and use a Python or a Shell script to download and install them in the actual development environment.
This isn't a good idea when you have many short-lived projects, but, in my case, the typical project lifespan is measured in decades and there aren't that many of them. So, I can expend the extra effort required to do that.
Unfortunately, I don't think there's a way to automate the process. The key point is that there's a human who sifts through dependencies and figures out what to do with them. Partially automate, maybe... but I can't think of a way to make this into a program that I could give someone.