I struggled a bit trying to obtain a keyboard setup for my US keyboards enabling me to use letters with accents. So I report my configuration for future look-ups. (Note: I use the left Window button to activate the accent feature)
This is the content of the file /etc/default/keyboard/:
XKBMODEL="pc105" XKBLAYOUT="us" XKBOPTIONS="compose:lwin" BACKSPACE="guess" XKBVARIANT=""