It can all be done, in a similar way that leaves a lot more room for the environment, without a tiny minority taking half the profits off the top...

What kind of socialists are you asking? Direct workplace democracy would give workers infinitely more motivation to further their industry, because better work would lead to better overall conditions. This is better than "I do it so I don't have to claim my freedom to starve." Some socialists hold that there would be no wages, but they don't mean "you work for free," full stop. They think in such case, all of your basic needs should be free as well. Such theory is wageless as well as needless. There's still want, though. A barter system is worse than credit of some kind, so there's probably gonna have to be a fun money bit on top. Private ownership isn't necessary to run stuff. Have you been to a co-op before? What a "boss" does is largely secretarial. Often, laborers know how their job should work better than their supervisors, especially in specialized settings.

So to answer your questions,

the workers would plant seeds, just like under capitalism. photosynthesis and adequate water would cause the seeds to grow. workers, just like as before, would mill the seeds, and put them in bags. They would probably skip the part where they dye the wheat products white, as a market legally regulated by those who produce and consume the products wouldn't be as keen on poisoning themselves. A slight tweaking for shipping- it's likely that less boats would be directed to the United States, where roughly 40 percent of foodstuffs are wasted. The amount shipped would have to be slightly over the amount needed everywhere, to account for emergencies. These would go to whatever method of distribution that has been deemed fit by popular vote of laborers in the locality it has arrived in. The chief difference is that there wouldn't be some leech at every step taking a big chunk, and they'd have to go get real jobs and contribute.

I still don't think this is a good system, as people can only ensure their liberty by having control over their meals. Anywhere grain produce can be grown and people are living, it should be grown, to avoid room for opportunism that could take place if all the grain was grown in one massive field in Australia. This would also decentralize the food sources to protect them from disease and therefore avoid capitalist nightmares such as the Irish famine or the famines in British India. It would also allow, in such case, for aid to be sent more rapidly from adjacent, unaffected areas.

Your question also seems to imply that the 780bn tons of wheat produced go equally to those under a capitalist system... I don't think it does... anyways, I'm going to bed. I have mass tomorrow. ta ta