okay so.. This is gunna be a really noob question

How do I get more of these? I've bought all the ip icons + crate https://gyazo.com/a7949782ef596b813c67f5b2e24ac308.jpg Do I have to buy these now or can someone explain how I can get another chest frag? https://gyazo.com/a66d16a4072779e7305f1aa02ce4f5ec.jpg Cause from the 3 icon chests I received enough to create a single chest And from this new one the 1500 IP icon + chest I got two fragments

If I need to buy chests I don't mind but I'm just confused as to how this all works ( I only JUST got used to hextech crafting lol.. )