Final answer:
The exact most important trading partner of Flanders by 1300 is not provided in the reference material, but historical context suggests the Dutch or the Burgundian domains are likely candidates due to Flanders' significant role in European trade and textile production at the time.
Step-by-step explanation:
By 1300, Flanders was experiencing substantial economic growth, contributing to the development of a robust trading network across Europe. While areas such as Italy, particularly Florence, and the Hanseatic League were key players in the revitalization of European trade routes, the most important trading partner of Flanders during this time was not explicitly mentioned in the provided resources. However, considering the historical context and the emergence of the Dutch as a significant trading power, it is plausible to suggest the Dutch or the Burgundian domains, which controlled Flanders at the time, could be among Flanders' major trading partners. During the 13th century, trade networks were expanding and Flanders, known for its textile production, became a crucial center for commerce in Northern Europe. The exact trading partner of Flanders is not clarified in the reference material provided, but by piecing together the historical data regarding trade in Europe, one can infer the importance of the relationships between the regions mentioned.