Its not doable if the wooden poles can't reach the bottom. They also decay.
You could consider using stone posts instead.
But heres an example as its doable for sure and fun looks great.
https://quoramarketing.com/wp-content/uploads/2021/02/Valheim-How-to-Craft-Beehives-to-Harvest-Honey-400x300.jpg
Check out Yotube
https://www.youtube.com/watch?v=FYM9w2gyYb0
Open Chrome then type in search Valheim Stone Bridges click on Images. These can give a lot of inspirations. Use any words to decsribe what your looking for images are awesome.