Get some agar flakes from the organic/green shop or even the chinese
supermarket.

These are used by the tissue culture people to make the gel that the
plants grow on in laboratory. Also other nasty things in the hospital
labs.

Agar is also used for jelly making amongst other things.

An odorless, tasteless, 100 percent vegetable gelatin made of a
variety of wild sea vegetables/seaweed. Check out 'Agar Agar flakes'
on Google.

Just make it a bit more watery than you would in making a jelly.