If you want absolute safety then look at anything from a "protected" zone (sub-30) to another protected zone. There's a run from Villanelle to Solis that's about 5g and takes 8 Cherries and 50 Dried Flowers. With a donkey or a couple of lucky carriages it doesn't take too long.
Somewhat more hazardous but I see a lot of people doing it is a run from Hasla to Villanelle using the air transports. Takes 30 goose down and 50 medicinal powder and is apparently worth about 10g. But you have to go from Hasla to Rook to Falcorth to Villanelle. Takes a bit since you're reliant entirely on the air transports. Make the pack during peacetime Hasla (which is quite often).