I found a quicker way of getting this.
* Buy 1 deadly spinner trap
* Go down to the main arena and press Y to access the build menu
* Hold LB and choose the deadly spinner trap you just bought
* Put the ghost of the deadly spinner trap over a pillar or wall so that it's RED (not white)
* Hit A 2 times
It's important that the deadly spinner trap ghost is red so that it doesn't build, but for some reason, the game still counts it as one built.