Create a Spec Template
Configure a spec template that you can leverage in your Style specification as you build your style.
Navigate to Site Settings > Style > Spec Template
To create a template, fill in the necessary details in the popup
Size Scale is a field needed to be configured in the Site Settings as well
Reference Size field will depend on the selected Size Scale
Click 'Create' to save initial spec template details
Once the template is created, continue building it by adding your sketches and measurements. Click 'Save' to complete.