Take a tray big enough to hold the lard slices flat in one layer. Cover the bottom with a little olive oil. Season lightly with sea salt and generously with pepper and rosemary leaves, then lay the fat on top. Repeat the oil and seasoning process, then leave for up to 1 day in the fridge. Arrange the fat curled on a plate like rose petals. Grill slices of bread. Serve the olive nectar separately.