Choose Format - Arrange - Send to Back (LibreOffice Writer, LibreOffice Calc).
Choose Shape - Arrange - Send to Back (LibreOffice Draw).
Shift+ትእዛዝCtrl+መቀነስ ምልክት (LibreOffice ማስደነቂያ, LibreOffice መሳያ)
Open context menu - choose Arrange - Send to Back (LibreOffice Impress).