2015 Scion FR-S with

this is poking from the wheel well at stock height by about 5-10mm in the front. In the rear it's probably going to look pretty much flush at stock height.
so picture mine with a meatier tire, and 9mm further out from the wheel well (which it is already 5-10mm out already). Lots of poke in the front.

In order to avoid so much poke on stock suspension, you have a few options. 

Stretching the tire is an option I suppose, but the wheel is still poking the exact same amount, its just the tire might make it look a bit closer to the wheel well. It's not going to look great, I don't like the stretched tire look, I really don't like it with stock suspension. Personal preference. My tires are more stretched than I wanted... think its the brand of tire really.

The other option is to add lots of camber. Hard to do with stock suspension. Again at stock height this might look sillier than if it were the same car lowered. But an option none the less. 3 degrees might work.

You might be able to have the backpad of the wheel machined by 10mm. But that's going to cost money to have it done properly, you had better love those wheels because now they're custom and if you ever break/bend a wheel you're going to have to get the same process done to them next time.

The last option, and the best option IMO is to get a different wheel with a higher offset. At 18x9 and stock height, I wouldn't do any more than +42, maybe +40 if you're doing 255/35/18. If you go any higher you will hit the struts/springs. This will still poke, like my picture above, but not as offensively as a +33.

If you are set on those wheels with those tires, either lower it and add a bit of camber, or just deal with lots of poke.