The installer registers the Slate Desktop installation with the Windows Programs and Features control panel (or Add/Remove Programs on older versions).
There's also an uninstall.exe program located in the application folder, C:\PTTools\System\slatedesktop. The installer also creates a shortcut to the uninstall.exe program in the Slate Desktop start menu folder.
Bug in Windows 10? For some unknown reason, Windows 10 shows the uninstaller in the start menu shortcut one time. If you click on it, nothing happens and Windows 10 hides the shortcut forever, even after uninstall/reinstall.