My thoughts on ramps:
At least 8" wide (10-12" is better for two way traffic),
cleats at a 4-6" spacing, angle 30-40d off horizontal.
They can climb
up a steeper ramp, but may avoid it coming down.
All the bottoms of my ramps are 16" above ground/floor, they can jump that easy and often jump/fly higher. This lessens the angle, shortens the ramp material needed, keeps wood off ground, and keeps floor space clearer.
Main run ramp is all 1x lumber(2 pieces tied together with cleat fasteners) and a 3/4 plywood platform(I call this the 'porch').
Brackets on coop wall above are for an awning to protect pop door from the weather.
Ramp on secondary run is 5/4 deck boards with 3/4" cleats.
This one is a little steep (board lengths were scraps) but functional,
lots of room to fly down.
Smaller 'training' ramp is all 5/16" laun underflooring,
mostly used indoors only used here a week or so for chicks to get the idea.
These are 3/8" plywood with 3/4" x 3/4" and 3/4" x 1/2" cleats.
Little tiny broody nest ramp made from various scraps.
It was
really cold and I did
not want them to get stuck outside of nest.