I have a component that works if I call it in app.html but cause error on other pages - Uncaught (in promise): Error: Template parse errors: 'coupons-list' is not a known element: 1..
Are you already using Ionic 3 with lazy loading? So perhaps you have to import the custom component into your module file for that page!
Yea, thank you. Forget about that 
If your custom component is fairly heavy, you may want to know that you now have a separate copy of its code in your app binary for every page that uses it.