Hello,
I am in the process of building a desktop made from a walnut kitchen counter top. The dimensions are 1500mm long by 620mm wide by 40mm thick. (59 inches by 24.4 by 1.57) Sorry, I'm stationed overseas at the moment.

The shelf will be made out of the same material but only 30cm (11in) wide with two uprights like in the picture. The uprights will be cut off the end of an extra piece of the shelf, length tbd.

Question: Using a Kreg Jig with appropriate length screws. Would it be advisable to screw into the cut off upright pieces? My idea is to place the screws like the red lines in the picture. I would then like to attach the shelf to the worktop, again using the kreg jig.

Or can you provide another solution for the uprights?

The tools I have available are:
7 1/4 Circular Saw with a Diablo 60 tooth blade, 1/4 router, Kreg K5 jig, drill, jig saw, a chisel, and a sander of course.

Knowledge: 4 years of wood shop in high school 19 years ago.....

Thank you for the help,

Randal Ogozalek