The Layout Manager
Configuring the FlashBB layout is literally as easy as drag-and-drop. The layout can be separately saved for each user, and the default layout can be set by the FlashBB administrator.
Below I have logged in as the admin, and set up a special layout that hides the Utilies and Info Panes, and moves the Categories & Forums pane to the right side of the screen. When a Forum thread is clicked, it will appear in the large area at the left.

Now, I'd like to save this layout as the default layout for all new users. Keep in mind that users can change the layout for themselves after login, but they will see this default layout initially. First, click on the Panes Manager button on the main header bar.

If you are logged in as an administrator, then you will see a new button, "Save", on the Panes Manager window. Clicking this button will save the layout as the default layout for all users. The Panes Manager can also be used to open any previously closed panes.
Let's take a look at the "flash_user_config" table in MySQL again (you may recall this from the installation page). In this table, there is a "-1" user_id value. This corresponds to the default layout. Then, there are integer ids for every user. In addition to the pane layout, the chosen theme and "look" is also saved for each user.

It naturally follows that if you'd like to reset the layouts of all users, then you can simply empty this table, and re-save the default layout. It's not recommended that you edit this table. Let FlashBB do it for you. Also, since the layout and theme for any particular user is saved by User ID rather than, say, IP address or a browser cookie, it follows that the user must be logged-in before seeing their custom layout.