Step 1: Create a Postage Category
Log in to Toggle and go to Settings > Postage Categories.
Click Add postage category and set:
Category Name: e.g. "Free postage (internal fulfilment)"
Service: "Other"
Tracked?: "No"
Click Add.
Step 2: Create a Postage Option
Go to Settings > Postage Options and click Add postage option.
Configure the settings:
Postage Category: "Free postage"
Fulfilment Provider: "Dashboard"
Internal Reference: "Internal fulfilment"
Price: £0.00
Leave Max Product Quantity/Value blank.
Set Live? to "Yes".
Click Add.