In my last session, I had to prod them a bit but my players thought things through and came up with some clever tricks while defending a fort. One of my players, an Investigator archetype from MFoV, used Reverse Gravity to get to the roof along with jars of hot oil. Another player had two ideas, one was to take a bed and add wheels, shielding, and spears around it. The part Barbarian kicked it down a path at some enemies, almost killing three enemy soldiers and doing major damage to a Gryphon (I rolled a Dex save for him and he failed). Another was for her familiar to take a beehive, wrap it in cloth, hoist it from the roof, and drop it when enemies got close. Finally, the last trap was a light ballista, intially aimed at the door but then moved it when they realized the Barbarian in the way. While simple, it worked well and they knew to move it out of the way.