Honeybees festoon and draw their wax honeycomb down from the comb guide in the center of the foundationless frame's top bar. They draw out a few of these palm sized combs on each frame and keep drawing them wider and wider till they all merge together into one single comb that spans the frame from edge to edge. One of the two most crucial aspects about foundationless beekeeping concerns the frame's end bars and is detailed below.
The Crucial Step: Narrow Frames
The trick to reducing cross comb with foundationless beekeeping is shaving down the end bars so the width is exactly 1 1/4". I've got a jig that is permanently mounted to a router that removes 1/16" of wood with each pass. I run each end bar through the router twice. One pass on each side. This is very fast, precise and works well for me. When I first started I used a simple hand plane and a set of dial calipers to shave the end bars down the right size. Whatever you do, be precise about it. Don't just knock a little off each side and call it good. Measure and make sure it is 1 1/4" wide. If you mess up or disregard this crucial step you will regret it. I promise.
Don't be a victim of Group-think!
In this photo notice the triangular wedge shaped comb guide in the center of the top bar. This comb guide is where the bees will draw the comb down from. A lot of people out on the Interwebs recommend melting beeswax on the comb guide. With the FF Method it is not necessary whatsoever. I've never ever done that and my bees center on the comb guide with no problem.
Pro Tip: If you have extra time and want to really stack the deck in your favor spend your time narrowing your end bars to 1 1/4" wide and verifying your hive platforms are perfectly level instead of melting wax on the comb guide.