Freelensing is a form of photography where the lens is hand held in front of the body and is not inserted into the bionet. If you ever tried it, it is pretty cool and creates tilt/shift like effect, only with a random aspect to it because you are… well… hand holding the lens. This is why it’s called Freelensing.
If you are new to the subject, or just want a refreshment, Luke Roberts has a great introductory tutorial on freelensing (which is where the title sketch was taken from).
One of the harder things to do while freelensing is focusing, you are constantly moving, the camera is moving in relation to the subject, and the lens is moving in relation to the camera. This is where Magic Lantern can help. Magic Lantern is a custom firmware pack for Canon DSLRS which adds features to the camera.
One of those features is focus peaking, a feature which highlights the focused areas in the frame. So turning this feature on allows seeing when you are in focus. Here is a video tutorial on the subject by Chris Lambeth with this and other few tips:
[Using Magic Lantern For Free Lensing With Focus Peaking | Chris Lambeth, Freelensing | Luke Roberts]