I posted a simple hack http://community.carbide3d.com/t/nomad-cheap-and-easy-y-axis-slot-covers/1677 using packing tape to help seal the y axis slot openings as well as the to help seal the door. That worked okay but the y axis tape eventually deformed and wasn't keeping the chips and dust from falling through the slot and onto the table under the Nomad. So, I made some bellows type way covers using an air conditioner side panels.
Amazon link to the ac side panels here... https://www.amazon.com/gp/product/B007I7KMT2/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1.
The mod is relatively straight forward. I just built a simple wooden frame the width of the table and long enough to accommodate the full travel of the bed plus the compressed length of the way covers. It requires cutting a slot in the bottom of the door and a hole in the rear housing panel. I used 1/8 acrylic sheet to seal the top and bottom of the frame on each end. That's probably not really needed but it adds strength to the frame. I cut both of those using a table saw and a jig saw. I used VHB tape to secure the bellows to the bottom bed plate (NOT the black plate that bolts onto the bottom plate). When using VHB tape you should rough up the part surfaces and clean them well with acetone then apply pressure for a few minutes while the tape sets. The VHB tape has held up well and I can change out my plate for a spoil board without having to rebond the ways.
I also used some small wooden blocks and silicone to fill the large holes in the back rear of the housing. There are quite a few holes that go directly through the housing and to the outside and the electronics compartment. I didn't seal the hole in the electronics compartment because it needs a way to flow air that the fan pumps in. IMO, it would have been better to make that hole on the rear panel vs. directly into the work volume where dust and particles can migrate into the electronics. However, the electronics compartment wasn't all that dirty so for no more than I use the machine its fine the way it is.
This mod cuts the amount of dust that makes it onto my work table by about 90% but some still makes it through. That's good enough for me for now. I'm going to be adding a dust collection system so once that is installed I don't think there will be much dust to speak of anyway.