Or..... Or.....That is a good point that @CjH made, the soap pouches, great, it cuts down on plastic waste but the plastic bottles wouldn't address this issue, what about a pouch like some drinks come in, you know, with the straw? Something that could hold the splash untill you got it in the post and then was able to decant into your own glass bottle. Plastic free would be a big selling point in this day and age!
Just spitting ideas out there!
Cardboard containers like the other type of drinks carton. Just flatter.