There are many methods that work. Using bare forks to drag would be at the bottom of the list for the reason you described (truck slipping off the forks). Always refer to the manufacturer recommended towing procedure 1st and use that where applicable.
Myself, I fabricated a tow attachment that hangs on the carriage of a 6000lb truck that works for towing all but one of my 75 truck fleet.
Remember, if it seems unsafe it probably is.
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