Hello,
Yes, vertical facing would definitely help.
I had some difficulty getting a flat cut on the side edged and bottom end, and thought it was not going to be flush when gluing to the MDF base, so I opted for the horizontal layers. The obvious problem there is the warpage that naturally occurs with this stuff, which causes the gaps and seems. i have since figured out how to use my jigsaw to make relatively accurate 90 degree cuts in 2" foam, so that should not be a problem next time around.
When I get around to making more of these I will opt for vertical pieces or finding a supplier for larger solid eps foam blocks (I found a few but the cost is way too high).
I would love to offer more step by step wip shots, but often find myself pressed for time in the production line. At some point in the future I plan to be in a position to publish some good recources and recreate many of my past projects, possibly with a photographer on hand to help with the documentation. Hopefully I'll get to that point soon! It would be a very fun and rewarding project to make. The main challenge with doing that kind of stuff is just time and money. Once those things are aligned, great things always happen.
Much of what you learn as a terrain maker / model maker comes from techniques developed by your predecessors and peers. There are sometimes moments when you come up with something new, and it's great to be able to share those ideas with people who are excited about them. That is one of the reasons I post up my stuff here and there!