The phrase "basic skeleton" refers to the main structure or outline of something, without any additional details or specifics. It is like the framework or foundation on which you can build or add more things later. Full definition
«All of the new molecules are based on the same basic skeleton, with very small differences between them. (sciencedaily.com)
The molecules we have been working with all start with the same basic skeleton but we tweak them in different ways, so we make it a little bit bigger here, smaller there, we swap out a methyl group for a hydroxyl group. (brightfocus.org)
With the basic skeleton complete, there's an important step you'll want to take before you send the Page out to the world... or even your co-workers. (hubspot.com)