The flasher location varies year to year. In 2001, it was inside Aux Relay Box #1. Look for a black plastic box up under the dash to the right of the steering column. It is roughly 2"x2"x6" and has a snap off cover.
Look in my signature for a link to online Ford owners' manuals in English.
2003 FX4 Level II, Supercharged 5.0L V8, Headers, Duals
BW4406 manual transfer case, Aussie Locker, Torsen L/S, 4.10's
Bilstein 7100 rezzies, Cadillac/Mustang rear discs, Duff traction bars
Keypad Entry, Lock LEDs, ABS switch, sway bar discos
Heated seats, Explorer EATC, Trip Computer and consoles
2003 XLT 2.3L M5OD-R1 reg cab beater, 2011 Taurus SEL, 2016 C-MAX Energi Plug-in Hybrid