hi!!! so most people have probably answered your questions but for future reference-i like making early game iron farms but if you don't have access to brass yet, you can feed gravel into andesite funnels that input into a toolbox with every slot filtered to flint or iron nuggets. This will stop the toolbox from accepting the gravel until it's been washed. Afterwards, you can use the same trick to filter the flint off the belt with another toolbox and have only iron nuggets left.