Slake-line ( calcium hydroxide)/ water / terracotta / crushed red brick to prepare cement.
Roman-like since the ancient Romans used pozzolona ash, pumice, slake lime to prepare their cement.
The cement is ready for application when sticking to the trowel.
Top: the cement
Bottom: drying cement on a lower layer of dried Portland cement.
I will be preparing such cement with slake lime, water, pumice and fine sand to make a mortar.
Aggregates, of course, produce cement. Top layers of grout to the dried mortar followed by 'Fresco Secco" painting.