The problem with that type of aider is there's not much to hold it open. When you put weight in the lower steps. the steps above close, not leaving much room to get your foot into.
This exactly. All is well with a ladder style aider until you try to sneak your boot into the top step and it is shut like a clam.
The CAYG DIY aider I made works well enough that I no longer even think about making another.
They are pretty easy to make if you have the desire; mine is sewn but can be made with knots if you take your time and ensure you measured it correctly. The part about DIY aiders is ensuring you have exactly even spacing or it can be a strange experience coming down in the dark because for one (or more) steps you will keep reaching with that leg searching...
Mine has a single length of 1" tubular nylon running down the middle with (3) steps sewn to the sides in alternating fashion. Each step has a small (~2") piece of 1" flat nylon sewn into the UPPER portion of the step to keep the opening wide enough for my 13 boots and a length of 1" flat webbing sewn on the step itself as a stiffener. This foot piece extends up both sides of the step a little bit - that last part makes all the difference for me in keeping the step open. Because it is all webbing with no internal rope or other 'stiffener' it folds together nicely for packing.
My top step is a couple inches shorter than the bottom two steps to account for the placement on a WEI step because I use a hook from an old ratchet strap to attach it to the step I am climbing. I also have a length of 550 cord attached to the hook with a loop on the end so I can run my saddle belt through it; it cannot fall. When I install my next step I just pull up on the 550 cord and it lifts right off the step I am standing on. I have honestly NEVER had an issue at all with this aider.
You could easily make one to attach to any stick or step, there are lots of options. If I made one for sticks I would attach with a loop on either the versa button or preferably to the top of the stick if there is an part that protrudes vertically. It would be really easy to pull up for use on the next stick.
I would take a picture and post it but I am writing this while on a business trip in Amman, Jordan -- during dadgum archery season.