Cover the block with a folded towel or thick cloth so that you don't shatter the concrete when you strike it. With a hammer, give the covered block a smart blow. It should break into several uneven pieces. Create a path from the broken pieces. Now you can begin choosing plants.
Mexican sage is easy to grow from cuttings.
Before planting, soak plants well so that the roots are wet. After shaking the excess soil from the roots, place each plant in a crack between the concrete steppingstones, anchoring it with the bent wire. Reserve the excess soil. Place the reserved soil around the roots. Once the plants are where you want them, gently squeeze the concrete back together.