attempting to create exposed roots. HELP

I'm brand new to this site & have a question for anyone who can help. I'm attempting to make a couple exposed root (neagari) bonsai trees. 1 maple and 1 azalea. I built boxes for them. the boxes have slats that are about 1 inch thick so that, by removing the slats, I can gradually expose the roots 1 inch at a time. my question is how often should I remove the slats? without any knowledge or insight, I was going to try removing 1 every 3 months or so, but if anyone has any experience or knowledge it would be greatly appreciated. thank you.

You have the right idea, but I think it will be quite a bit less often than that, but it depends on the age of the plants you are working with, and whether they have some large roots to start with (and how large a bonsai you want to make with each).. A picture of each would help.

At each stage you would probably be uncovering the roots you plan to expose next to see if they have matured as far as you want, then covering back up if not. Depending on the tree (whether it can handle it or not), you might want to cut off a root (leaving a couple of inches) that is growing much bigger than others, to slow it down and create a fork. These kinds of evaluations and pruning will have an effect on the pace of progress.

This spring, inspired by Jonas Dupuich over at Bonsai Tonight, I repotted all of my conifers into colanders lined with window screen to maximize drainage and promote root growth. The trees seem very happy. What might be really interesting for an exposed-root project is to construct a tall pot using screen or some other plastic mesh. This might not only maximize drainage and promote fast root development, but you could cut away as much of the mesh as you want each time, giving you complete control over the root exposure rate, and limit the risk of exposing too much at any one time. Maybe I will try it. I was looking at chochubai quince photos online the other day and saw the most beautiful exposed root quince . I will post a picture if I find it. Speaking of exposed root projects, Mr. Dupuich has some cool setups for that as well:

http://bonsaitonight.com/?s=exposed

Are they're some different size rocks for the roots to twist and turn around on they're way down or just straight soil?

I was actually wondering the same thing. It looks like Mr. Dupuich does use a larger particle size for the exposed root projects, presumably to get the twists and bends he wants, but uses a standard mix at the top to support the current root mass when he originally pots them:

http://bonsaitonight.com/2013/03/26/repotting-1-year-old-black-pine-seedlings/

These pines are shohin trees though, so for a larger tree I assume you could use even larger particles. It would all be relative to the size of the tree. Interspersing some larger particles in with a more standard mix would allow the soil to hold enough water for the roots to thrive but would provide enough sizable interruptions to create the desired twists and bends. Although i suppose using just large particles would drain much faster and encourage faster root development, and would pull the roots downward and encourage them to lignify faster.

wow. a lot of info. the trees are pretty young. I do have several different sizes of gravel/rocks in with them. i'll try to get a pic up soon. I'm not good with computers so i'll need my wifes help & I'm not ashmed to admit it.