Some months back, I found a procedure to create a template for Avery label 8163 (2x4) so that we can make the print portrait as opposed to the default landscape. I actually had to create a separate template just for the portrait. I named the templates Avery8163-2-by-4 and Avery8163-2-by-4-P - obviously the “-P” for the portrait template. My problem… I HAVE NO IDEA WHERE I FOUND THE PROCEDURE TO CREATE THE TEMPLATE! 
I’d like to do the same now for other size labels, but I can’t find how! Can anyone please help??? Thank you in advance!
The default format for the 8163 label you quoted, and I think all labels, is Portrait, i.e. long side vertical. So do you want to create a Landscape label, long side horizontal?
My (very) little experience had me File, Save As…, File Type = Template from the dropdown.
I do not know if LO has a specific place to store templates as opposed to working documents.
The location can be found under Tools > Options > Paths. By default it’s a sub-folder of the LO user settings folder. (Version 5.4)
I will no longer use that feature. I had several templates that I had worked on quite a while to create and they disappeared the last time I updated LO (I recall someone else posting with the same problem but I couldn’t find the post using the forums sorry search engine). I’m now storing all my templates in a folder on my computer. Whenever I need to use a template, I just go to that folder, double click on the appropriate template and it will open in LO.
@LadyFitzgerald I’m not familiar with that problem, but I’d guess that’s because an upgrade somewhere along the line (probably from 3.x to 4.x) created a new user profile. But 5.x continues to use the same location as 4.x.
Personally, I use a combined solution: I have a folder in Dropbox where I keep my templates, and I also configure LO to use the same folder. Can’t lose it, and you can still access it from within LO!