Thanks , is there anything i can build that is safe for him to climb ?Welcome to the wonderful world of climbing RussiansThey are very good at it and love doing it.
Trying creating safer places for him to climb. Sink the flower pot into the substrate so there is a good depth of Substrate in it, but your tort can still get in then pile more substrate round the pot so that there is a more gentle slope.
Yes, tipping is a hazard and you just have to keep adjusting things to reduce the risk

Russians will climb and walk all day. It may just be that now he is comfortable in the enclosure he is ready to see what all is in there and perhaps on the “other” side of the walls.
Flipping can be a concern, particularly for hatchlings, but tortoises are quite good at righting themselves. I am not going to link to any here, as some people find them upsetting, but you can very easily find videos of tortoises getting back up.
You might try a rock that’s a good size; My Russian likes to climb large rocks and then slide down them. And I do mean large. Here she is next to or on a couple of her favorites. She skids right down the sides. Both of those rocks can be easily accessed from a lower/easier side, she’s not interested. It bothered me the first hundred times or so but it’s how they live in the wild. So maybe something that’s taller than your tortoise but with a more or less flat top and some edges he can get a grip on.
Did I read you have access to slate? Maybe you could pile two or three pieces up for him to scramble over.
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Thats what i will doI’m not sure I understand what this would look like. Is the box upside down? And he could walk up the ramp to the top of the box?
Seems reasonable enough.
I think I’d just put in a brick by itself to start and see what he does. You can bury it in the substrate if you don’t want it too high. Then start working on putting the box and ramp together.