Apparently part of the rush of putting these aftermarket slides and frames together is they use Glock parts and they are seen as improvements on the Gen 3 Glock? 
I put together a Polymer 80 pistol just to see if i could and to see how reliable they are. Turns out, it's pretty easy. I used some hand tools and patience to put mine together. Image below from TJ Parmele - Image Title: Polymer 80 "Glock" build
Image Info: Here is my completed Polymer 80 build. This is the finished product from an 80% frame build.

Image below from TJ Parmele - Image Title: Polymer 80 Project
Image Info: This is the standard product coming from Polymer80. This is their version of an unfinished "Glock-like" frame. It takes Glock slides and Glock parts. It comes with the plastic template, drill bits and the internet tells you what needs to be done where. 

Image below from TJ Parmele - Image Title: Polymer 80 "Glock" build
Image Info: Here is my completed Polymer 80 build. This is the finished product from an 80% frame build. 

I did this mostly as a proof of concept to see if I could pull it off. It's a nice shooter. I purchased the 80% frame from a dealer with cash. No background check was required. The only problem with this is none of the components are cheap. All said and done, it's cheaper to buy a used Glock LE Trade in. I like the pistol and it's fun to shoot. It even takes Glock aftermarket magazines. Just had to make a minor adjustment or two to make it fire reliably.