I would like to create an app that adds an additional section to the checkout page - a possibility to select the delivery time window. I know that such apps already exist but I want to use my own application server to generate the values that can be selected.
What is the best way to approach this? I've spent last 2 days browsing documentation and following various shopify tutorials but I'm still confused. I thought that application bridge would be the way to go but it seems that it only allows to embed application frame in the admin panel, not on the checkout page.
I would appreciate any advice.