The decoration steps are optional. You can serve the cake plain if you'd like. The decorations you choose are up to you and depend on your decoration skills. I piped a ring of the colored meringue around the top edge and bottom edge of the cake.
For the marshmallow fondant flowers, I used vegan mini marshmallows and powdered sugar. I actually always make too much of the fondant. I would recommend using ½ cup of marshmallows.
Melt the vegan marshmallows in a bowl in the microwave. Mix it every 20-30 seconds.
Once mostly melted, add in about ¼ cup of powdered sugar and mix until it becomes pasty. Then knead with your hands until it isn't too sticky to work with. Add more powdered sugar as needed. Also, not all of the powdered sugar will become incorporated into the fondant.
Divide it up into pieces for the different colors you would like to make. Knead in gel food coloring with food-safe gloves or oil your hands first. When mixing with bare hands, all of the dye washes out of my hands after a few hours.
Allow your fondant decorations to dry out in the fridge the night before you make the cake.
You can serve the cake right away or allow the meringue to dry out a bit overnight.