I will be refurbishing our 1930's balustrading in a few weeks time.
There is a nice solid oak handrail, but no spindles (ballusters) - the
original construction has solid oak newels and rail but the sides are
clad in plywood on rough timber carcassing.

I will be buying some white oak spindles and baserail - the latter will
come with fillets making spindle attachment easy. But I am unsure how
best to attach the spindles to the underside of the rail.

The rail has a nice flat surface - will it be OK to simply glue and pin
the spindles to this, or should I be thinking about cutting a rebate on
the underside and trying to make up fillets? Or some other method maybe?