You use The Bronze Rule, AKA the Fate Fractal, and treat those environmental factors/Aspects as characters, allowing them to make an attack (emphasis mine):
In Fate, you can treat anything in the game world like it’s a character. Anything can have aspects, skills, stunts, stress tracks, and consequences if you need it to.
This is called this the Bronze Rule, but you may also have heard of it as the Fate Fractal if you pay attention to the Internet. You’ve already seen some examples of this in other places on the site; you give your game its own aspects during creation, you place situation aspects on the environment as well as on characters, and the GM can let environmental hazards attack as if they had skills.
So, you roll whatever you'd roll to set the trap, which would be Create An Advantage to place the aspect "explosive runes". The bad guy walks in, and the GM treats the runes as a character, allowing them to roll an attack against the bad guy. What level should the runes' skill be at? That's up to you and the GM, although a quick-and-dirty way to decide is to simply set their Attack rating to whatever you rolled. So if you rolled a +4 to set the trap, it'd attack at +4.