The warlord was probably the mage that had the hardest time with the hex board if he was playing by himself, team games he was very useful due to thier being another mage to support him. But with the release of FIF and the change in ruling with the garrison post he no longer has any issues being by himself. Outposts have always been defended by walls and now it's very easy to have a dwarf panzer to be summoned to the garrison post by your barracks and then have your mage use the defend spell to put a guard token on him immediately, if you feel that your garrison post is in danger. I actually did just this on one of our games that we played allowed me to have enough time to have soldiers appear and have Talos summoned.
Here is a way to do walls on a hex map: put the wall on an intersection of three hexagons. it blocks two of those hexagons from the third hexagon, depending on how you orient it. When you extend a wall you have to check to make sure it touches the old one. the walls count as being in all 3 zones for attacks.
you could block off a middle zone with 3 to 6 walls, depending on the wall locations.
I believe Echephron explained walls perfectly. If you want more of a visual I can take picture and edit it for you just like they do in the core game rule book.