Get your fish a nice coffee mug to play in, and lots of silk plants.
If you get a terra cotta flower pot, be sure to enlarge or seal the hole at the bottom with aquarium-safe silicone, or knock the bottom out completely, making sure to sand any edges and corners smooth.
10g is a pretty big space for one betta and with barely any decor they can begin to stress due to the exposure, so by planting several silk plants fairly close together in the back, with the flower pot and/or coffee mug laying on its side will help give them security.
I have about 10 silk plants in my 10g: 3 large, 2 medium, and 5 small plants all placed from end to end of the tank, going from the middle to the back of the tank with some of the small plants in plastic drinkware, leaving the front clear for swimming space.
I also have a flower pot and coffee mug tucked under the plants, and a floating craft mesh tunnel.
You probably don't have to over-do it like I think I did though, I just wanted to make sure my guy had things to swim through or sit on at different depths of the tank.