The FIA Junior WRC regular won all but one stage across the weekend in the all-Ford Fiesta Rally 3 category despite experiencing steering issues on both Friday and Saturday.
Already carrying a comfortable 3min 34.7sec lead over second-placed Jan Černý into Sunday, Joona did not let up his relentless push and took a clean sweep on all four of the final leg's speed tests.
His win moved him within a single point of championship leader Sami Pajari, who was contesting the WRC2 category.
"The rally was quite okay for us," he said. "We got what we came here for and found things to develop in different areas.