Remove the stopper. Boil your kettle again and pour the boiling water down the drain. Follow this immediately with a steady stream of hot tap water for 30 seconds.
Pour 1/2 cup of baking soda directly into the drain. Try to get it as far down the hole as possible. Use a spoon or the end of a toothbrush to push any clinging powder down. clear blocked drain with baking soda
Boil a full kettle of water. Carefully pour it directly down the drain. This softens the grease, soap scum, and debris that is causing the clog. Wait 1-2 minutes for the pipe to cool down slightly (so you don’t melt PVC glue, though boiling water is generally safe for metal pipes). Remove the stopper