Spindle top design
I am making a spindle top for a cedar privacy fence. 1.5x1.5x12" cedar spindles, with 2x3 top and bottom plates. It will need to have the ability to rack slightly to match the T&G fence section below it following the grade. I do not want to simply screw through the 2x3 into the ends of the spindles since it will not keep them from rotating and will probably open up gaps over time. I prefer not to sandwich it and nail through faces like picture below because it looks bad and leaves gaps for water/debris. I have considered routing out a 1.5" slot on the 2x3 and sitting the spindles in it and then end screwing through the 2x3... but also gaps between spindles for dirt/debris/water to collect but not as bad as sandwiching. Also considering using drill press to punch 1.5" holes about 1/2" deep and then cutting out corners somehow, but having to do about 10, 8' fence sections would be a massive time investment.
Looking for ideas on not only best way to do this, but a way that I can do it with the least time investment.