White clover and most other legumes require a shallow sowing depth and can regularly be sown too deep when sown with other more tolerant grasses. The ideal sowing depth for most legumes is around 10 mm with good consolidation. They can be successfully broadcast but require good seed soil contact and some consolidation of the seed into the surface of the soil. See below for establishment considerations.
Understanding your fertility status early on is critical. Learn more about soil structure and fertility here.