Where can I locate junction boxes in attic? Above insulation?

I want to know where I can locate junction boxes (for housing wire nut splices from NM cable) in my attic.

My house is real old and has every kind of wiring I can imagine, including knob and tube. The insulation is very deep and covers the top of the joists below. I have dug through this to find the old wires and junction boxes. I never want to do that again.

I have vertical posts in the center of the angled roof rafters and I am wondering if I can have a few cables (say 4) run vertically up out of the insulation maybe one foot to enter each junction box secured to either a post or even a rafter near the edge of the attic.

Any other solutions to making the junction boxes visible and accessible above the insulation?

 

Posts and rafters are fine. Any cables in areas where you can walk should go through the center of ceiling joists not on top of the joists.

 

You could add small surveyor flags for any boxes that are buried under the insulation. I see no problems with the boxes on the trusses.