Based on the original definition from I2P homapage, a reseed server consists of a Java I2P router, an HTTPS web server, and some scripts that periodically gather router infos from the router, bundle and sign them into a custom file format, and deliver these files over HTTPS.
This tutorial will walk you through the process of setting up a reseed server and routing its traffic over Cloudflare. You may ask: “But why Cloudflare?