Buy a medium Reptile Carrier and place a Zoo Med mini UTH(Under Tank Heater) on the side. Cover the rest of the sides with some kind of background so that the frog cannot see out. Cover the vented lid with plastic wrap to hold in heat and humidity, but make sure to leave the vents on each end open for air circulation. This setup will be small enough so that the frog does not feel overwhelmed, but will also provide plenty of space for the frog to grow.

Use Coconut Fiber substrate only deep enough for the frog to cover itself so you can find it. Feed at night. These frogs are nocturnal. Try small crickets for now and when you offer him crickets break the hind legs off them so that they cannot jump. This will make them easy prey.

Try this and keep me posted.