This is a trap tile that I use pretty much anywhere i want to represent a spike trap that the players have found or triggered.
Start with a 2x2 tile. I use the 2x2 piece from Cavern Floor Mold #281.
Drill holes slowly and carefully into it in a random pattern making as many holes as you feel you need spike.
Raid your kitchen supplies and find some pointy tooth picks. Snap them into bits so that the pointy ends sticks out as far as you want your spikes to rise. Stick a dob of glue into each hole and then stick your pointy tooth pick into the hole with the pointy end up.
Wait for it to dry completely and then come back and fill any gaps between the base and the spikes with more glue. Repeat this process until there are no gaps.
Once completely try you can proceed to paint then to your preferred style. Dont forget to paint the tips with some blood red or poison green!