Creating
To create a MAF file, open Scrapbook and right-click on the desired entry in the sidebar. Select the new entry "Create MAF" to create the archive.

Scrapbook MAF Creator no longer creates the archive for the item you selected in Scrapbook's data directory by default. It now prompts you to configure valid path in the preferences dialogue.
You might like to check the Scrapbook data folder for a stored site before archiving and remove any files generated by Scrapbook CHM Creator and Scrapbook MAF Creator to avoid making the resulting file larger than necessary. To access this directory, right-click on the entry in Scrapbook and select "Show Files" from the "Tools" sub-menu. Alternatively, you can leave them there and have them archived along with the rest of the data. You can access the files later with a standard zip utility.
Multiple Archives
You can also right-click on the folders in Scrapbook's sidebar and select "Create MAF" to create MAF archives for all sites stored in that folder. You can use the preference setting "Store multiple sites in one archive" to determine whether all stored sites are stored in a single archive or each site is stored in its own archive.
Note: It should be pointed out that this extension does not create a fully compliant MAF archive. That's because it aims to do something that MAF itself doesn't do, which is to store all linked files in the archive rather than create external links to them. The extension is, in a sense, using Scrapbook as a vehicle to gather all of the files together before storing them in the archive. Some features such as metadata for history and scroll position are not implemented as they are not particularly useful in this context (and can't be read by the current version of MAF, anyway), and the internal structure is slightly different. The result is that this extension provides a partial implementation of the MAF standard which should work most of the time. I have found one or two cases where the resulting .maff wasn't opened successfully by Firefox for reasons I have not yet been able to determine. If you would like to create fully compliant archives, your best bet is to use the MAFF extension and save the target page directly from the web rather than use Scrapbook.