I create the bashed patch first, then run xlodgen/dyndolod/occlusion, then run synthesis. I find that there are a few records that dyndolod uses from the bashed patch, so the plugin order ends up being bashed patch, dyndolod.esp, synthesis.esp, occlusion.esp, followed by map mod plugins. Your mileage may vary! Here's the remind I wrote for myself, but keep in mind this is based on the mods I have installed:
PATCHING ORDER:
1. Disable map mods
2. Remove all dynamic patches (bashed patch, zpatch, synthesis, dyndolod)
3. Run blacksmith forge water xedit patcher, enable it
4. Run bashed patch, enable it
5. Run the "No Grass in Objects" grass generator from within MO2. Move the output file to the NGIO mod.
6. Then run SSELODGEN/Dyndolod/Occlusion, enable them.
7. Run zedit patches, enable them
8. Run synthesis patcher, enable it.
9. Run the standalone Experience Synthesis patcher
10. Rerun Nemesis and execute the vbs file for Engarde
11. Re-enable map mods