(Assuming you’re using dried bellflower root) Place the dried bellflower root in a large bowl and immerse in water overnight (8 to 12 hours). Drain away the water. Wash the hydrated bellflower root with 1 Tbsp coarse sea salt. (This is to minimise the bitter taste.) Drain away the water and squeeze the water out of the bellflower root. Set it aside.
Place the cucumber into a bowl. Add 1/2 Tbsp coarse sea salt. Mix them lightly and leave them for about 10 mins while waiting for the cucumber to release its water. Gently brush off the salt from the cucumber pieces.
In a clean bowl, combine the bellflower root, cucumber and the sauce. Mix them well. Garnish with green onions. Serve. It can be refrigerated for 4 to 5 days.