Test-stack your bricks and lay out your plant stand as you want it to look. Build the stand onto whatever surface it will eventually sit on; ideally a paved surface and not dirt. Pull your design apart, lining the bricks up in order for easy reassembly.
Read the directions on your mortar bag and mix the mortar in accordance with the instructions using your bucket. You'll probably need to reduce the given mixing amounts for your smaller project by dividing the manufacturer's measurements into cups.
Mix the mortar, stirring with with a triangular trowel. The mortar should have the consistency of ice cream--firm but spreadable.
Lay a plastic cover over your work surface so the mortar doesn't leak onto the concrete. Keep the stand close to the edge of the plastic so you can slide your finished stand out easily.
Lay out the bottom layer for your stand, placing 1 inch of mortar on the sides of each brick.
Lay a 1-inch layer of mortar onto the top of the bricks after the bottom is done.
Tamp the next layer of bricks into place and continue laying mortar and brick layers until you're finished.
Press a brick capping tool into the mortar under and between the last layer of bricks to give them a nice finished look.
Leave the mortar to set for one to two hours.
Brush off any excess mortar from the fronts and tops of the bricks with a wire brush and leave the stand to dry for 24 to 48 hours before placing any plants on top.