modeling a hand in blender from a base mesh

does any one know how you can take a simple base mesh of a body and make a hand one it from the arms because i cant figure it out

when making a hand, start with one finger, then duplicate it, position, and scale, for the other fingers. leave a little gap between the fingers, instead of just welding them together at the base. i’ll make a screen shot to show you what i mean…brb
(edit) so, these are just some quick sausage fingers, to demonstrate what i am saying, so, ignore the fingers. the way they are joined on the left is the correct way, in my opinion. hopefully one of these guys will correct me if i am wrong.

May or may not be the best solution, but i do the same as i find this to be the less complicated for me.
I model a simple finger, then duplicate it to obtain every fingers of the hand, tweak them a bit, then join them like this Modron showed too :

After that i extrude and always tweak the vertices to try to get the shape of the hand

Then i to play with the topology to make it so the extremity of the hand have the same amount of vertices as the extremity of the forearm, so they can connect without problems.
Can be a little bit challenging of you want to keep all quads, but if a few triangles are acceptable for you, it’s much easier.