aagh, I edited this on the instructables mobile app and its deleted the intro page, I'll sort it out when I get a chance later on..
photos and sketchup model here for now
Step 1: Get Wood
Get your pieces of wood cut ready, I'm using 4mm plywood which will give a final thickness of 16mm for the heart when assembled, I figure that's a nice size not too big but not so small it gets fiddly.
Cut 4 pieces, I then used a block plane to get them the same width, but this really isn't necessary as your going to be sanding them to size later anyway, so don't bother.
Step 2: Get into shape
Mark out the shape, using a ruler measure two points 40mm apart and mark them, then connect them diagonally as shown, then using your compass set to 15mm diameter draw a semi-circle from the centre of one of the marks to make the basic shape. Carefully saw the shape out and sand to the line if necessary.
Then you can use this first shape as a template to make the others, you will need 8 in total, mark them out but don't cut them out yet.