Gently soften the coconut oil in a double-boiler. You can do this with boiled water without putting it on the hob, you don't want to cook the oil.
Remove from the heat and whisk in the bicarbonate of soda
Stir in the essential oils
Continue to stir until the mixture reaches a thick, gooey texture (a bit like thick custard). This is to stop all the bicarbonate of soda from sinking to the bottom.
Pour the gooey mixture into a container (before it stiffens completely) and leave to cool. I used a miniature glass jar that I found at my mums house. Any small jar will do, just remember to sterilise it first.
Just a heads-up though - this toothpaste doesn't taste quite as delicious as it smells. In fact it has a very salty taste thanks to the bicarbonate of soda. It does take a bit of getting used to, but is ok after a few brushes.
Advice: brush your teeth naked. This stuff takes toothpaste stains to a whole new level. If you do get any drips on your top, rinse with soap and treat with stain remover immediately before laundering.