Installing screen protectors.

So I thought I would start a bit of an interesting conversation. Does anyone on this form actually know how to install a screen protector on an iPhone yourself? If you do, how do you apply them successfully? From what I understand, the new screen protectors that are being designed with the latest iPhone having an alignment tray. So I am wondering what is the best way to do it? If you do not install them yourself, do you typically have somebody installed them at say a cell phone store for you? The screen protector that I have on my phone was actually installed for me by an employee at my local target of all places.
I personally use an OtterBox screen protector, along with an OtterBox defender series Pro case for my iPhone 15 Pro Max.