Cat toilet and hygiene
A cat toilet and gravel are, in addition to food and water, the most important things you need to care for your cat.
Feral cats used soft soil and sand to cover their droppings to hide their odor from other cats and predators. It is a strong instinct and kittens are easy to clean.
Cats are - generally - very clean animals, so the litter box must also be clean and accessible.
Show the kitten the litter box as soon as it comes home so it knows where to go.
Whether you want an open litter box, closed or closed with a door is a matter of taste - the kittens are used to all 3 models.
I would recommend the Catit Jumbo cat toilet (approx. DKK 250). It is solid, spacious, has a high edge so that the gravel stays in the box, and it can be emptied without removing the entire top.
Buy a dirt mat in Harald Nyborg or similar to put in front of the hill - it will take the gravel that might get stuck to paws and fur.
Cat litter varies widely in quality. It pays to buy a good quality one, because then it is much easier to keep the tray clean and odor-free.
I use clumping cat litter and would recommend 2 brands.
One is Everclean - there are many different types, coarse and fine, with and without scent - the scent is only activated when the paws step on the gravel
I have tried most of them, and like the coarse grain Less Trail best. The other brand is the Classic brand. The properties are largely the same on the two brands. Classic is a bit cheaper, but is in plastic bags (a bit unwieldy), where Everclean is in cardboard boxes.
A layer of 10-12 cm must be filled in the litter box for a start, and filled as needed - remember to buy "dog bags" and possibly disposable latex gloves. Then put on a glove - root around in the sand, collect clumps in the dog bag - finish by taking the glove off and into the bag and tying a knot. It goes in ordinary combustible household waste.
Clean the tray twice a day - then the gravel will last in the tray for several months.