There is one big flaw in your plan, unless you finish a residency, you cannot take cannot take the State Board Exam, and you cannot get a License, if you don't get a License, then you cannot practice Medicine. If you get cause in your little "Doc in a Box", you will be put in jail for a long time. but otherwise, yeah, sure go ahead...
You have this a little confused. The State Board Exam is different from your Specialty Boards.
You can practice medicine as soon as you have an "unrestricted license." By having an unrestricted license, you are able to practice independently, as well as apply for a DEA#, which would allow you to write for narcotics and other controlled substances.
You can apply for an unrestricted license as soon as you have passed Step 3 and fulfilled the number of residency years that the state board requires. Most states require 2 years of residency at a minimum before you can apply for an unrestricted license, but some states still require only 1.
At the end of residency, you are eligible to sit for your "specialty boards." These are specialty specific exams that are administered by your specialty group. For example, if you finished a pediatrics residency, you can sit for the boards that are given by the American Board of Pediatrics. If you are a surgeon, you can sit for the boards given by the American Board of Surgery.
By completing a residency, you are "Board eligible"; by successfully passing your specialty boards, you are "Board certified."
You do not need to be either board eligible nor board certified to practice medicine independently. However, most reputable places, even in very rural areas, would prefer to have Board Eligible/Board Certified ("BE/BC") physicians staffing their clinics. It's also harder to get decent malpractice insurance without being BE/BC.
P.S. I have to agree with danzman, writing "M.D." behind your name when you are at least 12 years away from that point is....a little insulting to those of us who have worked incredibly hard to earn that title.