Roll out the red sugar paste to about 7mm (1/4 inch) thick.
Cut out a shape for the base of the boat.
From the offcuts, cut a thin strip that will act at the mast.
Roll out the yellow sugar paste to the same thickness and cut out two sails.
Finally, use the green sugar paste to make some portholes. I used a small piping nozzle to cut mine. Brush a little water on the back of the circles to help them stick.
Place all the pieces on a tray lined with baking paper.
Now, you can either leave your sugar paste overnight to dry, or you can set your oven to its very lowest setting and place the tray on the middle shelf.
After about 10 minutes, the sugar paste will be soft due to the heat, but it will have lost a lot of moisture. Don't touch it, just allow it to cool and you should find that it has become hard enough to hold its shape.
Make the sponges
Preheat the oven to 180C (160C fan, 350F).
Put the margarine, sugar, eggs, vanilla, self-raising flour and baking powder in a large bowl.
Beat with an electric whisk until the cake mixture is even and well combined.
Divide the mixture between two greased and lined 20cm (8 inch) sandwich cake tins.
Bake in the oven for 25-30 minutes until golden and springy to the touch. Place the cakes onto a wire rack and allow to cool fully.
Fill the cake
Place on of your cakes upside down on a plate or cake stand.
Pile half the jam on top and spread the jam to the edges of the cake. Spread the remaining jam onto the top of the cake.
Place the second cake on top (also upside down) and spread with the remaining jam.
Cover the cake
Roll out the blue sugar paste on a work surface very lightly dusted with cornflour. Aim to make it just slightly larger than the top of the cake.
Drape the sugar paste on the top of the cake. Allow the extra to hang over the side of the cake and shape it into ripples gently with your fingertips.
Complete your boat
For this, you'll need an edible glue. Place a small chunk of sugar paste (you can use your offcuts from the boat) in a bowl and add a few drops of boiling water, stirring until you get a thick, stiff glue.
Your boat shapes should now be set. Gently turn them over and use a little glue to bond the sails to the base of the boat.
Dab a little more glue along the edges of the sails and position the mast in place.
Place more edible glue along the length of the mast, then place a wooden skewer on top.
Leave to set. It might take up to 30 minutes. If you can't wait, you can use the same oven trick you used before.
Push the skewer into the centre of the cake to position your boat in place. And you're done! Time to serve yourself a well-earned slice.
Your sugar paste will need time to dry and harden. In the instructions below, I'll show you how to use your oven to dry it out. Alternatively, you can cut out your shapes the night before.Make sure to look through the step-by-step images to help guide you through making your sugar paste boat.