Screw wooden board onto concrete wall

I have a large window in the living room and want to install a wooden window sill on the concrete base. The wood is solid spruce, about 4 cm thick and 2.8 meters long.

I am now looking for a way to fasten the wooden plank on the base. I think 3-4 screws M8/M10 should be enough. However, I don't know which screws/anchors are best suited for this.

Important: the screws should be as inconspicuous as possible afterwards. Maybe there are even caps for these screws in the spruce color style.

Does anyone have tips on what I should look for to find the right solution?

Thanks and best regards

Do not screw at all, it will develop cracks there. Glue with parquet adhesive.

For example, Hilti screw anchors with countersunk head. Drill and then screw in the screw anchor with an impact driver. It doesn't get any easier.
6mm anchors are more than enough. Better put in 5-6. That will hold forever.
Cover the countersunk heads either with a plastic cap or preferably sawdust with wood glue. Then sand slightly.
Of course, pre-drill the wood.
The tip from is also good. Good assembly adhesive.

Simply glue. However, there are also assembly kits. If you use plugs on the concrete side, save the other side for the wood and then "slide in" the bench. But in my opinion, this creates a gap under the board.

Would also stick. There are enough products that make it permanently rock solid.

Thank you, one more important note.

Depth of the board = 25 cm
Depth of the base = approx. 15 cm

So I have 10 cm of the board protruding. It might be that adults sometimes sit on it.
It's not the ultimate leverage acting on it, but do you think gluing could still work? It would actually be the most convenient solution!