I need to show embeded slider (marked green) inside of the list of recyclerview items, like on image below:
I am thinking that I need to change something in my recyclerview layout manager, but I have no idea what exactly and guess it is quite complicated. In addition I am using FlexboxLayout here.
So, could you please help me with the selection of the best approach of solving this problem?

You can inflate different view for that position , since you're inflating a different layout there .
This answer will help :- RecyclerView with multiple view type
The basic gist is to use the getItemViewType and return a flag , say 1 for the first red box , 2 for the second and 3 for the third and inflate layout on depending on the viewType param ( in the signature )