Hi Shellee.
Although we no longer follow the rules of the Computer Braille Code, its 1991 (excellent!) supplement titled "Flowchart Design for Applicable Braille Codes" is the correct document to use to create a flowchart in braille. List the symbols on a Special Symbols page or immediately before the flowchart. Of course you will follow UEB contraction rules for any words in the chart.
Lindy