Flaxseed eggs seem to be widely used to avoid chicken eggs, by choice or following medical advice. I have no experience with the matter so I was perusing documentation in the inter webs to learn how to make them and how to use them.

That seems to be an easy task requiring just two ingredients as Jessica points out. Good point. It seems to be a quite easy process detailed by Clara in a short video, just in case text instructions are too complex for you to follow.

I took notes for my personal kitchen archive.

Use Linum usitatissimum L seeds (aka linseeds, flax seeds) thoroughly shredded to disrupt the testa and expose the embryonic tissues, the whole reduced to a fine powder. The finest powder you can achieve is to be used. A coffee grinder can be used if it’s not offended by linseeds. Mine cooperated after I threatened to smash it.

Add Brita filtered water (my tap water isn’t great), 1:3 powder:liquid, mix and incubate at room temperature (~22 °C) for 15 min. Viscosity doesn’t seem to increase after that period.
Some sedimentation occurs, so think about thoroughly homogenizing your preparation before sampling.

I’ll update after testing for conservation of aliquots at -18 °C.