Commerce Customizable Products is another module that provides custom line item types like Commerce Custom Line Items, which I've shown before.

Our goal here is to sell a T-shirt with a customizable slogan on it. This could be any customization, and there could be more than one field. Here's how we do it:

Enable Commerce Customizable Products.

Create a custom line item type which will have the extra field. (We wouldn't have to do this if all products in our store had this customization.)

Add the field to the new line item type. In this case it's a text field called "slogan".

Create...