Tensei Ouji wa Renkinjutsushi to Nari Koukoku suru (Light Novel)
Hiiro was reincarnated as the third prince of a tiny nation. In his search for a way to strengthen the country, he dabbled his hands in the omnipotent alchemy. Along with his modern knowledge, he improved the country’s production processes and introduced salt-panning. In this small land surrounded by larger countries and the threat of magic beasts, Hiiro declared before his despairing citizens that he will ensure them a prosperous life. “What I want is not just to save the nation. I want to create a better tomorrow for you all!” The nation-building of a small country by his own hands starts now!
According to anime planet, the light novel series is on going while the web series on syosetu may be on hiatus. This series wasn't easy to find online compared to other light novels but it scratches a kingdom building itch for me.
Date of publication: 2019
2+ Light novel volumes
Publisher: GA Bunko
Title: 転生王子は錬金術師となり興国する | Tensei Ouji wa Renkinjutsushi to Nari Koukoku Suru
Author: 月夜 涙（るい）[Narou publishing name] 月夜涙 [Bookwalker] | Rui Tsukiyo | MAL | Twitter
Illustrator: 新堂アラタ | Arata Shindō | Pixiv | Twitter
Publisher: GA文庫 GA Bunko (SB Creative) | Volume One at SB Creative
Bookwalker Series Page
MAL has no mention of this work.
The author's Narou page confirms his being the Rui Tsukiyo referenced in the MAL author entry linked above; the other novels match.
ANN has the illustrator as Shindō, while MAL uses Shindou. That's a stylistic choice in transcription.
@weasalopes Yeah, not everything can be found at MAL
I knew plenty of Rui Tsukiyo's works, but even I've not heard of this one before.
From an edgy revenge story, to an assassin story in another world, to funny hijinks with orcs and slimes, to dungeon building, to tales of veteran adventurers and mages, to a novel about becoming a pastry chef, among others. And now kingdom building, that's quite the repertoire...