Sometimes the design is carved into the clay and enameled and others are designed with the lines in the mold and the enameling is colored in !! I would say carved and enameled no matter the method to simplify !! Another method is the Japanese Moriage ware !! They used string or sometimes just clay dots to outline a form then the enamel was added,, but your vase does not look like it was made with that technique !!
Can you take a pic of the bottom please ??