Simple and direct:
* My favorite pastime is reading.
* Gardening is a relaxing pastime.
* Playing video games is a popular pastime among teenagers.
More descriptive:
* Spending time with loved ones is my most cherished pastime.
* Exploring new places is a thrilling pastime that keeps me energized.
* Learning a new skill is a challenging but rewarding pastime.
Figurative language:
* My favorite pastime is losing myself in a good book.
* For her, baking is a form of creative escape, a soothing pastime.
* The gentle rhythm of knitting is a calming pastime.
Context-specific:
* In the quiet of the evening, her favorite pastime was gazing at the stars.
* During his downtime, he enjoyed the leisurely pastime of fishing.
* The children found joy in the simple pastime of building sandcastles.
Ultimately, the best sentence will depend on what you want to convey about the pastime itself and the person engaging in it.