In my younger days I thought direct democracy was unworkable, but now I realise that might have just been my brain conforming to the bourgeois representative government status quo.
Obviously we easily have the tech to do DD these days, everyone has a smart phone in their pocket, we could do it instantly and on the go. But how you could manage a planned economy that way I’m not sure.
Here's how I think of it... every household determines their needs and wants for some future period, say the next year. You need X pounds of flour, Y new pairs of socks and hey, you'd like a new computer. Everyone submits their needs and wants for the time period. Then it's up to the central planners to make it happen as much as possible. Maybe you don't end up getting a new computer this year but you're in the queue and you end up getting one next year.
Basically the people let the central planners know what they want, directly. The central planners then take their cues from the people - not some central government - about what needs to be produced and they do their best to make it happen.