You need to stack thirty castle (stone wall) blocks, reaching 31 total health in the stack. As walls can only be stacked three blocks higher than adjacent ones, this requires at least a 2x1 pattern. It is possible to pause the game, create two stacks of 27 and 30 height adjacent, select the 27 height stack and cancel it (delete key) before unpausing. This way you can place a single 1x1 tower with no extra cost. As the achievement does not require building an archer tower on top, you can safely deconstruct it later on to retrieve some of the resources. Note that archers / ballista weapons built on top of this height gain a massive range boost (about 16 blocks for archers), making them a very powerful inland defense.
Tips
Workers become skilled if they work the same job for long enough.
Windmills STACK! If you put two windmills around a farming plot, they stack. It's a +3 bonus per windmill.
Ideal farming output diagram is below.
F-F-F-F
F-W-W-F
F-F-F-F
Fertility doesn't affect orchards as much. Minimum output is 31 (minimum fertility to place, master workers), maximum output is 35. Don't waste your very-fertile plots on orchards if you can avoid it. Farms produce 10 food on normal soil with no windmills, using 1 worker. Orchards produce 31 food on normal soil, using 3 workers.
TLDR farming: Put orchards on minium-viable farming plots, use fertile soil to make a big line of windmills+farms.
Some buildings require being near roads to be placed. However, they don't need to "stay" near roads to function. Place and delete roads (blueprints) as needed to get your ideal layout. Keep in mind that rebuilding structures is a pain if they get destroyed like this though.
Ogres target walls first, above everything. And they have a set-kill-limit. If you are too early-game to defend against viking ogres, but don't want them curb-stomping your economy, build a lot of low level walls.
Vikings are required to disembark on land or on a bridge. If you want a safe spot they can't invade, just wall off or moat-off all the land on one side of your island. Instant viking-proof flank.
Bigger houses are better in terms of working-bodies-per-non-working. The lowest level house holds 4 people and 1 food-courier. The manor houses 25 people and 4 couriers. Once you can build manor houses cheaply, replace all your hovels.
Various Steam Achievements
Complete the indicated task to unlock the achievement.