As a first step, pour 225 ml of warm water (approx. 35-40 °C) into a bottle. Then add a sachet of washing-up liquid powder (25 g). Close the bottle tightly and shake vigorously for approx. 10 seconds. The powder should dissolve in the next 5-10 minutes.
Sometimes it can take a while for everything to dissolve completely. Individual particles may take a little longer. However, you can use your washing-up liquid now without any problems. By the next morning at the latest, everything should have completely dissolved and turned into a gel.