Another micro-exercise that combines elements from mindfulness with nature is "Sit spot".
But you could also translate it differently, namely in the sense of "Sit & Spot", i.e. "Sit down and observe".
This exercise sums up both very well.
For this exercise, look for a place in nature that is as beautiful as possible, where you are undisturbed for a while. If you don't have much time, you can even do the exercise in your apartment in front of a window with a view of the garden.
Turn off your phone, sit down comfortably, and then... you don't actually do anything.
Except to unintentionally observe what is happening around you.
After a while (about 20-30 minutes), the wildlife will have become accustomed to your presence and the animals will resume their normal activities.
You will be surprised at what there is to discover.
During my biology studies, I once did an internship in the field of crane conservation. We sat in a fixed place in the car all day and watched the cranes.
After an hour or two, the world around us suddenly seemed to awaken. Everywhere there were suddenly animals to be discovered that were not there before. Foxes, martens, lots of birds, everything suddenly seemed to come alive.
A truly wonderful experience that I still remember fondly today.
Simply sitting in nature is not only a great experience, you are also doing something for your relaxation and your physical and mental well-being.
Because spending time in nature is simply good for you, as a whole series of Studies confirmed.
The fact that you just sit there unintentionally during this exercise without having to do anything concrete can cause your stress level to drop and you to recharge your strength.
Together with the effects of nature on our well-being, this makes this exercise a true "relaxation booster". 
By the way: You can also take a photo of "your" sit spot. Especially if you have been to this place several times, such a photo acts as an anchor for the feeling of relaxation associated with the sit spot. So you can also put yourself back in this relaxation from home - simply by looking at the photo.