Thanks to Mosaic Art Now for posting this up. The video showing the sinopia (painted guidelines) found under one of the Roman mosaics found at Zeugma. It is mentioned at 9:35. Again this is sinopia found under a square shape border (swastika meander) rather than a curved shape such as any of the guilloche patterns.
At 10:45 you can also see hammer and hardies in use cutting more tesserae for the work.
Go to 14;25 for a list of the constituents of the original mortar.