Like
@freedoctor17 mentioned, you either do everything in one foundation area (12 units + research), or do a foundation + application, with things split between both (6+6).
I know people who have done both, but defining what the "typical" student does is a bit hard due to the flexible curriculum causing so much variation outside of everyone finishing the same core curriculum + scholarly concentration reqs. Even those things have many ways they can be approached - you can take Step 1 whenever you want and take as long as you need to study for it, you have the option to take MS2 over 2 years (1.5 days/week) while doing multi-year research etc.
Essentially....
The scholarly concentration reqs are more minimums rather than maximums. One of the unique things about Stanford is you're free to register for
any course across the university as p/f (so not just auditing but having it on your transcript, but with zero pressure due to no grades). You're given more than enough elective credits to take whatever you want and while you have no obligation to beyond meeting the scholarly concentration reqs, most take advantage of this since its pretty amazing to take stuff you're interested in to learn and explore, especially after years of worrying about As through premed. There's nothing stopping you from taking more courses in your scholarly concentration, courses in other concentrations/offered by the medschool, or even things like the biodesign courses done with business/engineering students (very popular, and have produced many projects that have been funded and brought to market), intro (or advanced!) compsci courses etc. The curriculum is designed to give you time for this and research - you have
every Wed off during MS1-2, and no classes after noon on Tue/Thu all of MS2 + MS1 after Q2.
Same deal with scholarly concentration research. You have to do a project that for most corresponds to 1 quarter full-time research over MS1 summer. You're however given five quarters full-time funding through MedScholars and while you could use this to extended your scholarly concentration research, there's nothing preventing you from using it to fund things completely unrelated to it, and many people do so.