Raising plant baskets

I have to plant baskets of pond plants along the margins of a large pond. My problem is that the pond level is too high for the recommended plant depths in the baskets so I will have to raise them on something. The pond has a butyl liner so it musn't be anything that may puncture it.

I was think about resting the planted baskets on bales of hay/straw on the marginal shelves. The pond has koi carp in it so I am not sure if this will damage them or the natural balance of the pond.

Any advice would be very welcome.

Thanks

 

Brick (as required) wrapped in off cut of liner.

Hay / straw may float, may not but it WILL rot

 

Done the same when i dug mine, bricks are the answer, my plants are in quite large pots. so the bricks do not stick past the pots, just in case the fish get spooked and bump into them.