Best way to fit decking handrail and spindles

Hi, am just about to fit the handrail and spindles to my new deck & was just wondering what is the best way to do it. they are the traditional type hand/base rail with infill & square spindles.

Should I make up each section first, screwing the spindles from underneath and then fix each completed section into place between newell posts or should I fix the hand & base rails in place first with all the spindles inside & then space each one out with the infill? I think I would rather do it the latter way but just wondering how I would fix the spindles in this way, - maybe screwing in to the rail at an angle?

Personal preference I think.
I fit my posts, deck round them and then make my hand rail separate.
I cut the rail at the desired measurement and then calculate what distances the spindles need to be apart and mark the top and bottom hand rail where the spindles will be fixed, you can then see if everything looks right before you put it together so you don't make any mistakes. Once that's together I screw through the bottom handrail into the decking and into the newel posts and fit a second top handrail to hide all the screws.
Hope that helps.