If you do not have the center console, then it's as simple as removing the radio trim (it unsnaps by gently pulling from the top left and right corners, then sliding fingers down the left/right sides). You will then see two small bolts that hold the cup holder tray from the center dash.
I'll guess center floor console type equipped Fords are the same.
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2005 F150 STX Regular Cab (4.2 liter V6)