Place the octopus, flour, and coarse salt in a bowl and rub vigorously until it becomes elastic and the mud is removed, then wash.

Yeonpotang (Clear Octopus Soup)
A recipe for Yeonpotang that brings out the clean, refreshing broth flavor and the tender texture of the octopus.
What You'll Need
Instructions
Rinse the cleaned octopus in water and drain.
Remove the innards of the octopus or leave them as is, then season with a lemon slice, soup soy sauce, and cooking wine.
⏱️ 30m 0sSoak the clams in cold water with coarse salt for at least 30 minutes to purge the sand.
⏱️ 30m 0sSlice the radish thinly, place it at the bottom of the pot, add the purged clams and rice water, and bring to a boil.
Cut the napa cabbage, green onion, and water dropwort into bite-sized lengths.
Skim off any foam from the boiling broth with a strainer.
Add the napa cabbage and green onion to the pot, then add minced garlic, salted shrimp brine, soup soy sauce, and cooking wine to boil.
When the cabbage is cooked, adjust the seasoning with salt.
Add the seasoned octopus one by one.
Top with the prepared water dropwort and boil briefly to finish.