In Prismic, Slices are reusable custom components defined in the CMS with specific content fields. Slices can be stacked and re-ordered on-the-fly as needed. Individual pages can be constructed using these reusable components to create unique layouts.
Think of them as Lego blocks for websites.
With this technique, traditional CMS functionality with multiple templates, one for each page type, becomes unnecessary. Instead, a single template with logic to render Slices as requested can be used. This reduces technical debt since each block of content has a single source of functionality and styling.
Slices are componentized so individual slices can be made in isolation from eachother.
For more technical information on Prismic Slices, read Prismic's official Slices documentation.
For instructions on creating a Slice, read the Create a Slice guide.
Before writing code, a proper understanding of the Slice's purpose must exist. Slices are typically horizontal content areas of a page that should be reusable on any page (with the exception of visual design incompatibility).
The following questions come to mind:
How will the slice act with other types of slices above and below it?
Slices may need to interact with adjacent slices. For example, elements may stylistically extend outside the Slice's container and overlap content above or below. Or the slice may need to include a top border if it follows a Slice of the same type.
Slices can be styled with the surounding context in mind using CSS with adjacent or sibling selectors. This is an advanced technique that should be used infrequently as it may cause unexpected results when building new pages in the future.
What kind of stylistic variations will this slice have?
Different pages may require slight tweaks to the coloring or positioning of the Slice's elements. Providing different "styles" or "themes" selectable in the CMS can help in this case.
Minimizing the number of variations makes development easier and causes less confusion for clients. If you find yourself making a large amount of variations, consider breaking the Slice into multiple Slices with distinct names.
Will this slice be reused anywhere else?
If the answer to this question is no, a traditional Slice may not be the best fit. Instead, a project could contain an "unconfigurable" Slice that allows the user to select from a list of pre-defined components to insert in that Slice's position. This Slice would see the component selected and insert it directly without any custom data from the CMS.