FlytrapCare Carnivorous Plant Forums

I want to make a water tray out of a sheet like in the attachment but I'd ideally want to avoid killing all my plants this way
Is it safe?

It can, but if it is a product that is meant to be used in a wet area and handled by people, it is generally safe. Unfortunately, and chemicals that may leach out are unlikely to be measured by a TDS meter, so eyeball it.
If the water begins to gave a chemically smell, or you see an oil sheen on top, I would discontinue using it.
Another option would be to set it up, fill it up with water, and don't use it for a year. Let any bad stuff happen without plants, then maybe use it. Just a thought.

Doesn't seem like it's worth the effort, I think I'll settle for a pool liner or something similar. Thanks!