Peel the sweet potatoes and cut them into rough chunks.
Place the chunks in a pot and cover with water.
Bring the water to a boil over high heat.
Reduce the heat to medium and simmer until the sweet potatoes are tender and can be easily pierced with a fork, about 15-20 minutes.
Drain the sweet potatoes in a colander and let them cool slightly for about an hour before mashing. Mash the sweet potatoes in a bowl and add the flour, soy sauce, cinnamon, and salt.
Mix until you have a uniform and slightly sticky mixture. If the mixture is too soft, add a bit more flour. I like to mix with my hands to ensure all the flour is fully incorporated.
Shape the mixture into small patties (about 15) with your hands.