I have a simpler option to the other answers, it doesn't work in all situations, as it can use a little more room. And as you can see only works where you can insert onto the start of a belt from 90 degrees.
An inserter cannot pick something up that's moving directly away from it on a higher tier belt.
With the below fast belt going up. The standard inserter at the bottom of a fast belt won't be able to pick anything up until the belt is full.
I use it for stocking up Logistics Chests with e.g. ammo from my military science pack production line.
It works with either Fast Belts, with standard, long or burner inserters. Or with Express Belts with any inserter.