"What other warning signals does the 777 give, apart from the stick shaker, when an aircraft is this low, slow and high AOA?"
There is a plethora of clues. We practiced this on the 777 sim with an autothrottle failure after the Turkish accident as well as being shown the FLCH trap.
The following clues are shown on the Primary Flight Display.
Normal pitch is around about level on approach. The pitch gradually increases, up to about 10 degrees when you get very slow.
The airspeed trend vector indicates a decrease in airspeed will happen.
The airspeed decreases.
Yellow bars start to appear on the speed ribbon.
Below those are red bars
Once you enter the yellow bars you are unable to apply any more nose up trim as the aircraft understandably thinks it is not a good idea.
The pitch limit indicators appear. If your pitch reaches them you stall.
On the central Eicas a low speed warning message appears with an aural warning.
The stick shaker goes off.
Any pilot familiar on type gets very uneasy very early on and would take action to recover at the first clue, throw in jetlag and delayed reactions and it should still happen by the second or third clue.
The problem is all this is happening around about 200 feet at a point when one tends to transition to looking forward at the runway with occasional glance at airspeed and rate of descent. Not being aligned may well have been an additional distraction.