Floating shelves are more popular nowadays. It's not surprising, because they have modern look, no visible brackets and they are pretty cool.
I'm presenting my way to make floating shelf. It's very easy project and don't require special brackets - just board and quite big screws - that's all. It can be placed on wooden, brick or concrete wall. I don't think however that it will work for drywall, but I don't see even commercial brackets for invisible shelves on drywall.
Step 1: The Board
Shelf could be made from any type of wood, but I recommend at least 1.2 thick, dense wood. Plywood is'nt the good idea.
First You need to cut proper/needed/desired shape. If You don't have power tools it's no problem. Use handsaw. If You are worried that Your cuttings wouldn't be straight, You can make saw guide from small straight slat, like I did on the picture/video.
Step 2: Preparing the Wood
Raw board should be sanded. Start from 120 grid and end with 400 grit. I also recommend to sand the edges, especially those one which You've cutted with handsaw ;-)
After sanding, put the protective/decorative coat on Your future shelf. I've used mineral oil, but any type of resistant layer will be good. So You can use any paint with any laquer.
Step 3: The Bracket/hanger
And now the most important thing to do - the invisible brakcets. I've made them from pretty big screws (at least 0,4inch in diameter and 5 or more inches long). I've just cutted the top of the crews and.. that's all.
Step 4: Hanging Floating Shelf on the Wall
You have shelf and the cutted screws. Now it's time to hang it on the wall.
Take the drill and make 3 holes in the board. Then put in those holes the screws. You can glue them using some strong glue like poliurethane glue.
Now draw straight and leveled line on the wall in the place You want the shelf to hang. Than mark 3 drilling points matching the screws in the shelves. LIke on the picture/video. Drill them and then just put the shelf with the screws into the holes on the wall.
That's all. Now You have Your floating shelf hanging.
In case If You are warried about stablility of such hanging, I ensure You that it will sustain pretty heavy things. I made such shelves in my kitchen. The most wide one has more than 1,2m wide and it is floating on the wall since two years.