I already have really short hair (I had a punk buzz-cut and am growing it out, how it's like a TWA/VERY curly pixie cut), and I wear very natural makeup where it isn't noticeable (maybe a sheer peach color on the lips is visible), and I have curves, but they're easily hidden by clothing (unless I wear like, a leotard and tights; I'm petite with a hint of curves).
I absolutely love baggy vintage Levi's, boyfriend jeans, Dr. Martens, Canvas sneakers, flannels, and crop tops--I wanted to wear a high neck halter crop top with boyfriend jeans, a flannel and converse, but am afraid that people will think of me as butch or lesbian, instead of just relaxed and comfy.
Most Helpful Guy
can't go wrong with sweatpants and a hoodie (depending on the weather) you can get away with the baggy sweatpants but a hoodie that fits just right won't make you look 'butch'. Also tied back hair (if shorter) or long hair add to that relaxed look
Most Helpful Girl
I also often have a relaxed/boyish style and my golden rule is: always wear something tight with something baggy. So if you're wearing a loose t-shirt with flannels, wear a skinny jeans or a high waisted boyfriend jeans with the t-shirt tucked.
Or wear a crop top with a baggy jeans (the outfit you described sounds really cool).
Also, a little makeup will also help (not extremely noticeable, but a bit of mascara won't hurt anybody) and long hair.
However, I think the golden rule is already enough if you have a curvy body and don't be scared to be labeled as a lesbian. Lesbians are cool and there are enough guys who like a grungy girl.