Foolproof, and very satisfying
The "instructions" consist of a few images on the box, similar to the image on Zooplus. I didn't really follow these and had no idea how much water to use. I later saw 'www.catit.com/uk/senses-2-0-grass-planter-getting-started' which is completely different!
Nevertheless 3 days later the seeds began to sprout, and after another 3 days lush green grass was plentiful. I left it too late to put the mesh top on, as it grows so fast. There is something strangely therapeutic about watching it grow!