Log Horizon, Tensai Ouji no Akaji Kokka Saisei Jutsu Recommendations
Tensai Ouji is not an isekai but I found the MC's in both of these have somewhat similar traits. In both they are slowly building and strengthening a kingdom and both are super clever and cunning type of guys.
But then again, Log Horizon is an isekai but back in the day they knew how to make one.
Log Horizon is the better one from these two.