Importing a single page
Admins can import single pages from Notion into Slab. Within a page, click the ... menu in the right-hand corner. Click Export. In the pop-up window, choose HTML and click Export. Make sure to toggle on Include subpages if you want to export those as well.

Importing all of your content
Admins can also import all of your content from Notion at once. In Notion, click Settings & Members in the left-hand menu and open Settings. Scroll down to Export, and click Export all workspace content.

Choose HTML and click Export.
Then, go to Import & Export in Team Settings. Next to Notion, click Import. Drag-and-drop the HTML file from Notion, or click to upload.
