If you are really concerned about it, I would check with a LOCAL CPA or tax lawyer.
As for me, I believe in KISS. I doubt that you are going to make enough money to call it a living wage selling scroll saw projects.
Unless you are out peddling product other than a flea market or craft show now and then, I wouldn't worry about it. If you are collecting sales tax on each sale and REPORTING it, or have a SEPARATE bank account for the business, then you may have a real concern. (paper trails are hard to shake)
I was in business for 20 years and had to jump through ALL of the hoops including paying both my half of SS (and being a one man business) I had to pay the employers half as well!
I had my phone number displayed on my tool truck and someone turned in that fact to the phone company and my home number became a BUSINESS number which of course is more expensive.
These days being a retired hobbyist I don't concern myself with all the hoops. Someone sees one of my projects and wants to buy it, I sell it at a reasonable price for CASH! (or personal check) No sales tax or business account for checks or credit cards. If someone wants me to make something special for them, I quote a price or ask the person to provide the materials and build it. (If I'm so inclined)
Granted, I don't make much money other than pay for materials and maybe $5.00 an hour labor and go on down the road. I do have some business cards that I give people who ask for them but, that is the extent of any ADVERTIZING that I do. It is tough trying to get business and stay out of the limelight at the same time.
Anytime you start making a lot of money or cutting in on someone else's business, you are subject to being reported to the IRS. I would think the if your making that much money or taking that much business away from others, you wouldn't mind jumping through all the hoops.
Rog