Place the almond milk and coconut oil in a pan and heat gently until the coconut oil has melted. Remove from the heat and check the temperature; it shouldn't be so hot that you can't comfortably hold your finger in it, otherwise it can kill the yeast. If it is too hot then set it aside until it has cooled to lukewarm.
Meanwhile, place your flour, yeast, sugar and salt in a large bowl. Yeast doesn't like to touch salt directly so add them on separate sides of the bowl, then stir it all together and make a well in the middle.
Pour in the cooled coconut oil mixture and add the lemon zest, mix it all together with a wooden spoon until it comes together into a rough dough.
Tip it out onto an un-floured surface (you don't want to add extra flour and make the dough too dry) and give it a good knead for about 10 minutes. It should be sticky at first but become smooth and elastic as you knead it. A dough scraper comes in very handy here! You can also pop the dough in a stand mixer to knead instead if you prefer.
Once kneaded, shape the dough into a ball and place in an oiled bowl. Cover and set aside to rise for about two hours in a warm place, until doubled. You can also place it in the fridge to rise overnight if you like.
Punch down the risen dough and knead briefly to burst any big air bubbles then roll it out on a lightly floured surface to an approx 12x18 inch rectangle. If you are struggling to roll it out and it keeps springing back then let it rest for 10-15 minutes and try again.
To make the filling, stir together the cornflour and lemon juice in a bowl until smooth then stir in the blueberry jam and lemon zest followed by the fresh blueberries.
Spread the filling in a thin, even layer over the rolled out dough then carefully roll it up from one of the long edges into a sausage.
Use a sharp knife to carefully slice the log into nine pieces then arrange them cut side down in a 23cm/9inch square tin lined with baking parchment. This bit is quite messy so if you lose any filling just spoon it back into the rolls once they are in the tin.
Cover with clingfilm and set aside to rise for about 1 hour, until puffy. Preheat the oven to 180C/350F/gas mark 4. Bake the risen buns for 30-40 minutes, until the internal temperature reaches 94C/201F on a probe thermometer. Cover them loosely with tin foil partway through baking if the tops start to colour too much.
Leave to cool in the tin for 30 minutes then carefully lift them out using the baking parchment and place on a wire rack.
To make the glaze, sift the icing sugar into a bowl and gradually stir in the lemon juice until it forms a thick but pourable glaze. Drizzle the glaze over the tops of the buns and serve. Store any leftovers in an airtight container for up to two days.