IOS: How to “unsnap” a slide over app
The OP is talking about an old iPad so mentioning “split screen” will not be available. Something like the mini 2 which is what I have and I have the same issue. 


Start Safari as normal so this is the main app.
Start Notes by dragging it from the dock and onto the right of the screen so this becomes the Overlay.
Swipe Notes right and then have a full screen Safari.
Swipe from the right to bring back Notes in overlay


Great but now I want Notes as my full screen app

If I swipe Notes off to the side it just hides it. It does not remove it the Overlay mode so if I now swipe up to get the dock and select Notes it comes out as an Overlay, not as a full screen app.

Various solutions I found are:


As OP said you add a different app as an Overlay. But I do not want another app in Overlay 


Or


Go to Home screen so no apps in view and then start Notes and it’s full screen but it secretly knows it is an Overlay so workflow is.


In Notes full screen
Dock to select Safari so get Safari in full screen as any other app would do
Dock to select Mail and glorious full screen Mail appears
Home button so no apps in view
Select Notes from Dock to get Notes in full screen


You have to do this extra step of going to the Home Screen for Notes (the was used in Overlay mode and ios11 is stubbornly not letting go) because if an another app is full screen then Notes will come back as Overlay. For clarity any other apps you could switch to using the Dock would be full screen so yuck for this




Or (homing in)


Annoyingly you have to have started Notes once in full screen mode to use this slight improvement as you bizarrely need that step to get the Overlay app to appear in the multi-tasking view so follow above to get that.  


Use can then use the multitask control panel. 
Swipe up to middle of screen and switch to Notes using this makes Notes full screen and as long as you switch via this back to Notes it is always full screen. 
So any other app you can switch anyway you want but always use the control panel to switch to Notes. Probably the most doable solution until you get an app to replace Notes in Overlay.



But one more I found


Kill Notes and start from Home Screen


swipe up to middle of screen to get the multi-tasking panel.
swipe up on Notes to kill it. As before for Notes to appear you needed to do the start Notes with no other app in view at least once.
Now crucially go to Home Screen so no app on view
Start Notes and it will be full screen
You can now switch as if it was never an Overlay



If you do the above but having killed Notes then go back to an app (Safari) and select Notes from the Dock then not only does it stubbornly start in Overlay mode but it also again does not appear as an app in the multi-tasking view.

I would like a list of apps in Overlay so I can switch between them. A clever version of the list we used to have and then swiping an app out of that list could be used to remove from a Overlay. At the very least it seems a bit of a bug that an Overlay app doesn’t appear in the multi-tasking panel until you started as view screen using hack above.