Complex sentence: Each flag is broken into its respective components, which are then categorized according to several broadly descriptive terms; users may pick and choose from a menu of these components to form a new flag, which they may then save to the site.
Split into simpler sentences: Each flag is broken into its respective components, that are categorized according to several broadly descriptive terms. Users may pick and choose from a menu of these components to form a new flag, which they may then save to the site.