Mowing every 3 weeks is generally a good practice for clover to keep it “low” and promote lateral growth rather than vertical growth. However, allowing some flowers to bloom can help attract pollinators and enhance its spread through seed production, as you are doing this year. It's important to find a balance; you might consider mowing when the clover reaches about 6 inches in height, which can maintain density while allowing it to flower intermittently.

Ensure that the clover receives adequate moisture, especially since it thrives in well-drained, moist soils. However, keep in mind that white clover does not perform well in dry conditions or sandy soils, as it prefers constant moisture levels.

Since clover is a nitrogen-fixing plant, it typically requires less fertilization than grass lawns. If you're using clover as a companion to grass, ensuring that it gets the proper nutrients (especially potassium and phosphorus) can help its establishment .

As clover can be sensitive to broadleaf herbicides, you should focus on manual weed removal or spot treatments for any broadleaf competition. Keeping the area well-mowed also helps reduce weed establishment.

 If you consider overseeding in the future to maintain or enhance the lawn, doing so in the late summer (between July 25 and August 15) would be ideal for Minnesota climates.

 Lastly, ensure your soil pH is optimal (around 6.0) and consider testing for nutrient levels occasionally to help monitor the health of your clover and any accompanying grass.

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Overall, it sounds like you're on the right track. Continue nurturing your clover with mindful mowing practices and moisture management, and you'll likely see successful establishment and growth over time.