I would use wheel chocks on any trailer before un-hitching from the vehicle. You will never know when the trailer will roll.
My standard practice is to put a wheel chock in front of one wheel and a wheel chock on the rear of the opposite side on flat ground. If I am on a slight rolling hill there will be chocks on the two wheels that are facing down hill and then two in the other direction of the trailer.
I will then lower the front legs on my 5er and un-hitch the truck and pull the truck away. I will than install a set of x-chocks between the tires to help eliminate the bouncing of the trailer from walking and than lower the remaining legs. The slides will then be extended after all of the legs have been extend and trailer leveled to prevent frame twist from the slides being extend before leveling.
Our ride is a 32 ft. Class C Motorhome with 2 slides. Does the same apply?