Strongest joint solution for stool with 2 legs

[Handplanesandmore]

You would be wise to chose something else for your first project.  What looks simple is in fact not.  You will need very well fitted finger joints and, unless it's for a child, likely thicker stock of a different species.  


John

......and be sure a) the child is a small one and b) while sitting, she or he is not "restless."


Simon

[Handplanesandmore]

if i were to do this, id look into doing steam bent laminated legs.

Yes.....Ikea Pello armchairs use that kind of leg. Close to a jointless design as opposed to the zig zag chair, but very strong.

[Cooler]

The zig zag chair by Cassina is the closest I can think of for the loads this would have to carry. 

Here is a video showing how it is made.  Copy that and you are probably OK.  The video is very interesting to watch even if you are not building this type of chair.  Actual production footage in one of the more sophisticated furniture factories in the world.  This construction may be outside the reach of a beginning woodworker though.


https://youtu.be/EWF4RLAsciQ



But note that the joint is the full width of the chair and in the original post each leg is just a few inches wide.  I would find that joint to be highly suspect.