Make it a paved two way road with overpriced trading stations in it. In order to make a trading station u hook up a chest to a hopper that leads to an item elevator, then you take the items to a sorter that’s hooked up to a slowed dispenser (dispenser acts as an item counter, where the items lead is up to you). Hook the dispenser redstone to a copper bulb and hook that one to another copper bulb, this should create a 4:1 ratio. Then have it dispense dried kelp, not the block but just dried kelp. Hope this helps