Interlocking is about preparation and grading. Laying stone and design always comes second. What we mean by this is that the grading and level of your project determines the flow of water, and how long your project will last. The better base the stones are on (large layer of crush runner, screening + compaction), the better result you will have now and 10 years + from now.
A poorly graded and prepared job can mean costly repairs if the flow of water is towards your house, or possibly costly repairs to relay the stone in the future. That is why we always tamp our projects with our plate tamper, and lay at least 6 inches of crush limestone before proceeding with your job. We lay landscape fabric to prevent weeds from coming, and drainage pipe where necessary for drainage.