We have developed RepTiles, a system for generating traces of random DNA for synthetic genomics applications. The system uses synthetic random DNA domesticated using the Phytobricks syntax. RepTiles has a base DNA collection of 52 1.7 kb chemically synthesised mini-chunks. This has been domesticated using the Phytobrick assembly syntax and is intended to be used with the Golden Braid assembly standard. RepTiles also has a user-friendly web application that facilitates the design of DNA assemblies based on the base collection. The system generates assembly plans for generating chunks using Golden Braid. The resulting chunks can then be assembled into megachunks using Transformation Associated Recombination cloning. It thus supports the generation of ultra-long synthetic DNA from phytobricks, contributing to the vision of synthetic plant genomics from modular parts to complete genomes.