Trays of flats are primarily used in the bedding business to:

Trays of flats serve multiple functions in the bedding business, contributing to the efficiency of various processes related to plant cultivation and handling. They are primarily utilized to grow tiny seedlings into usable size plants, which facilitates a more manageable planting process instead of using individual pots. This method allows for better space utilization and simplifies watering and maintenance.

Additionally, trays of flats are designed to hold individually potted plants, making it convenient for growers to organize and transport these plants, whether to distribution points or customers. This is especially beneficial in commercial settings where large numbers of plants need to be moved efficiently.

Furthermore, the trays also play a key role in handling logistics, such as transporting plants to a customer's car safely and securely. The design of these trays usually allows for easy lifting and carrying, minimizing damage to the plants during transit.

Thus, the primary purpose of trays of flats encompasses all these aspects—growing seedlings, facilitating convenient handling of potted plants, and aiding in transportation, which justifies the selection of all included functions in the answer.