Think about how much time it is going to take you to learn how to deploy and maintain your 'free' certificates and remember time is money. What do you make an hour? Is that more than the cost of a paid certificate?
I have used these certificates - https://cheapsslsecurity.com/comodo/positivessl.html - on multiple sites and it is very fast and easy. Other vendors sell them too and are likely just as good. Gandi do them too (at a slightly higher cost) and are the fastest method for me, though this may be because I have all my domains there already: https://www.gandi.net/ssl/standard?currency=USD#single
Don't waste hours chasing down free certificates when paid ones are so cheap now. Use Let's Encrypt only if you need lots of certificates and the paid options become prohibitively high.
I'll use Let's Encrypt when they have a easy setup available.
Use something small like https://github.com/kuba/simp_le or https://github.com/diafygi/acme-tiny
Note that the update process needs to be automated because let's encrypt certificates last only 3 months as I have read.
Started with Let's Encrypt. Running Mac OS X. Failed. Guessed cause has something to do with macports vs homebrew and having the proper Python version active. Disabled macports. Now the app runs.
But I got "Failed to connect to host for DVSNI challenge".
Start googling, reading, messing around with this for a while. No joy.
Bailed on Let's Encrypt, started over with StartSSL, because its the first source of free for not-for-profit certs I found.
Happy to take recommendations for alternatives.