How to avoid soft bottom of home-made bread?
The bottom of your bread looks a little underbaked, by maybe 5-10 minutes. You can see that the crumb is tighter A few tips:


There is no need to keep the dish with water in the oven past the point where the crust of the bread is set. It is possible that water vapour from the dish interferes with the bottom of the bread cooking. Try taking out the water when you drop the temperature of the oven.
Times in bread recipes are a guideline, not a rule. If your bread comes out (a little) underbaked, put it back in the oven and/or adjust your cooking time next try. When you put the bread back in, you can also put it in upside down to encourage the bottom of the bread cooking properly.
To encourage the bottom of the bread cooking, you can use a pizza stone/steel, or even a baking tray. Leave it in the oven while preheating, then put the tray with the bread on top.