If you don't have a dumbbell stool, you can try to replace it with other solid furniture or objects. For example, you can stack several benches or planks together to form a bench press platform, which can support you. Ensure that the platform is stable enough to avoid accidents in the bench press.

For the upward inclined bench press, you need to choose a slope suitable for your height to keep your head, shoulders and back on a comfortable plane. You can use some cushions or books to adjust the height.

In addition, you can also try to use your own weight to tilt up and press. Put a solid object (such as a solid chair) on the floor, then put your hands on this object and your feet on the ground to form a human slope. Then practice according to the correct posture of leaning up and bench pressing.

Finally, if you want to strengthen the upper chest muscles, you can try some other exercises, such as parallel bars arm flexion and extension, flying birds and so on. These movements can help you exercise your upper chest muscles better.