When cats lie back with their legs open, it is a sign that they are comfortable and feel relaxed in your company.
Photo by Niklas Hamann/ Unsplash
Sprawling their legs out like this makes them vulnerable, especially when their tummy is exposed. They will only adopt this position when they are absolutely sure that there is no threat around. If your cat does this often, it means they are likely very comfortable in your home and are probably pretty content and relaxed in general. So good job!