HTTPS for subdomains

Hello,
I’m launching a SaaS app soon, my domain is grapeflow.com, I’ve built the landing page using unbounce.com, so the landing page is hosted on unbounce, I’ve directed the subdomain get.grapeflow.com to unbounce, now, I want to get HTTPS (the green lock) on the landing page that is hosted on unbounce, and the app.grapeflow.com that will be hosted on our private server, what should I do?
Does Cloudflare provide me with a certificate for all of my subdomains regardless of where they’re hosted?
What is the lowest cost possible to do that?

Many thanks!
Al

The simplest way is to set SSL to “Flexible”. But it’s not the moral thing to do. You should create Cloudflare Origin Certificates for both servers, install them, then set SSL to “Full”.