This video doesn't have any good voice-over (it was early days) but the word bubbles will lead you through the steps for this great fun project. Remember the method is the same no matter how you would like it look as an end product.
Step 1- Biscuit Base: Finely chop 200gm white soap
noodles; add 40ml vegetable oil and 100ml water
Microwave 100% for 2 minutes, stir with a wooden spoon, and then at 60% power another 2 minutes.
Mix in 1 teaspoon cinnamon and 1 tablespoon wheatgerm.
Line an 8 inch cake tin with baking paper for easy removal later.
Spread the soap mixture into the base, leaving it rough on top.
Step 2 - Lemon Filling: Finely chop 400gm soap noodles;
add 80ml vegetable oil and 200ml water.
Microwave 100% for 2 minutes, then 60% for 2 +2, stirring with a wooden spoon between each time.
Add the yellow dye to get the effect you want, less is best, you can always add more.
Stir in essential oil, lemon would be the choice here.
Spread over the base, again leaving it rough on the surface.
Step 3 - Cut: As the soap cools you can cut it into pie shape wedges as in the picture.
It is much simpler to cut carefully when it is still warm; remove when cold.
Step 4 - Piping: Mix 400gm finely chopped soap with 80ml vegetable oil and 200ml water, then microwave as in Step 2; stir in the essential oil.
Put this soap into a piping bag and pipe onto each slice separately.