A mould should be made and and sat on a table or bench. A mix of 3 sand, 1 small Pea shingle aggregate, and 1 cement should be tipped in. The surface the mould is sitting on should then be vibrated to get all the air out of the mix. If this is not done properly, water will find its way into any pockets of air and, in the colder weather, freeze. Frozen water expands which makes hairline cracks in the concrete which gathers more water etc etc...Go to our projects section, via the link above, and read our project on Freeze Thaw action. Patterns are pressed into the concrete either my using a mould with the pattern in the bottom of it, or they are pressed into teh wet, but drying, concerete surace using a pattern block.