The light should be one of those standard long white neon tubes. In the animated gif you can also see the very light shadows in the other direction.
The wooden bars parallel to the lamp cover the light in its full length, while those orthogonal to the light tube cover only a small width. That's why the first are much more visible.
If you turn the table by 45° the shadows should form a rather even grid.
It doesn't really have much to do with a double slit experiment, which is used to prove a wave character. This appearance can also be explained purely with the particle character of the light, as light from the lamp can reach every part of the low shadow area in a straight line.
For the double slit experiment the slits have to be sufficiently narrow and on the screen behind it you will find maxima in places where there is no straight path to the light source.