There is a simple Android App available to conveniently upload files from your android devices. Combined with a scanner app, this allows to very quickly scan single page documents like receipts.
The project lives at this repository on github.
The app is very simple:
Add a new one With the Plus button. The name (A-1) is to distinguish it in the list. The url (A-2) is used to upload files. You can add multiple URLs. You can give permissions to access the camera and use (A-3) to scan a QR code from the screen.
Tapping an item in the list switches the view that shows some options. You can set one URL as the default (C-1). When uploading a file, the screen to choose an URL is skipped then and the file is uploaded immediately.
Other actions are editing the url (C-2), going back (C-3) or deleting the item (4).
The screen (D) shows a default URL with a green background.
Use some other app, for example OpenNoteScanner, and share the resulting files using the Share With menu (E). Then this app opens and uploads the file to your server (F).