Even with free hand embroidery, get the right stabilizer underneath. it makes a world of difference especially if you don't have the option of using a hoop. I started gluing the fabric to the stabilizer (washable school glue) instead of trying to move a hoop around, or trying to keep the fabric tight so it does not pucker.
You can do some really neat stuff that way. I have a vintage Singer book for doing free hand embroidery, and it's got lots of detailed instructions and projects. And it's all about doing it on straight stitch machine. Though with today's stabilizers (including wash away) some of it's a lot easier to accomplish.
This is the book I have, since copywrites have expired, you can get affordable copies now. I have an original for my collection. I know nothing about this site, linked only to show the book I was talking about.
Singer Instructions for Art Embroidery... book by Singer Sewing Company (thriftbooks.com)