I made initial contact with their HR dept by applying online and having a friend who works at the company give my resume and cover letter to HR. They contacted me to schedule an interview at their headquarters in St. Louis, scheduling was very flexible and compensation for gas was provided. Upon arrival, I was sat in an office where I took 3 different tests. The first test was a mental alertness test. Second test was a physics-based mechanical aptitude test. The third test was tool recognition where you were given pictures of tools and you had to name the tool and list its use or function. The first two were timed tests. I was not interviewed by HR but by the engineer I will be working under. He was more interested in previous hands-on experience as well engineering and design experience. I brought a project portfolio which helped a lot in showing my previous projects. None of the typical strenuous interview questions were asked which was a relief. I was supposed to be interviewed by multiple engineers but the others were out of the office. Since I was one of the first interviewers, I was told that I should wait up to two weeks to hear back but I was contacted the next Tuesday (interview was on a Friday) with an offer.

TL:DR there were 2 interviews and a mechanical aptitude/tool test, whole process took about a month. I approached a recruiter at the career fair because I thought their presentation board with all the tools and gadgets looked cool. I sent a follow-up email to the recruiter the next day saying I enjoyed meeting. Two weeks later, I was contacted to do a phone interview. The phone interview was behavioral and pretty relaxed. The next week, I did a Microsoft Teams interview with two engineers, one of them being my manager. They wanted to hear a lot about my projects. The last step of the interview process was a 20 question test with some simple but deceptively tricky physics problems, and a 15 question tool-identification test. I got an offer about two weeks after that.