N 400 form, self-employment or employer or skip it

I set up a S Corp in 2017 after getting GC and I am the only person for this S corp. To fill the employment history section of N 400 form, should I select self-employment or employer or skip the period I work for this S Corp?

I didn't get wage from my S Corp, but filed Schedule K in 2017, 2018, didn't file Schedule C.