There is one detail that we often struggle with in construction and that is the dreaded double plinth! The best option is to use wide bed plinth stretchers and plinth stretchers with the reference PL3.1. The ‘.1’ part denotes a 9mm upstand which must be used for the detail to work. The other common plinth special is a PL3.2 with a 23mm upstand which will leave you an unsightly detail that may cause problems with frost.
If you cannot wait for wide bed plinth stretchers (not many factories make them as standard) you can use another course of PL3.1’s but make sure you include a packer at the pack.