DIY alignment grid for my yoga mat?

Yo,

So, I'm poor and in a part of the world that's not really into yoga, which results in me practicing with YouTube videos and without access to sophisticated equipment. I'm a bit anxious about getting injured and trying to do all that I can to avoid that.

I saw that in countries better than mine you can buy ''smart'' yoga mats with alignment grids on them. Do you guys know of a place with instructions on how to make (by drawing the grid on your own mat) and use one on your own?