Ease into the tin, pressing evenly into the corners and sides – you can be rough with it. Spoon in the spinach layer, smooth the surface, then repeat with the barley and finally the squash layer. Dome the squash mix slightly to give a rounded top. Roll out the remaining pastry to fit, brush the edges with some egg, then press the lid over the top. Trim the excess and crimp or pinch to seal, then decorate with pastry trimmings cut into leaves (add bay leaves, if using, when the pie has 30 mins left in the oven). Can be covered and chilled overnight.