How can I create an L shape with two beveled sides? I've been trying to get this right but it seems like I get stuck every time.
This is what I'm looking for, but time and time again I've been stumped.

I have to add this boolean difference to it when it's sculpted out:

But when I go to sub surf it, this happens and it becomes very difficult to add loop cuts around them to fix it, actually they don't even show up at all and using the knife tool is too difficult.

Here's a cruder but see through version of the shape I'm looking for.
You can do this with the bevel tool.

Start with a cube, in edit mode (TAB) select the edges you want to make round:



press CtrlB to use the bevel tool and set the parameters for Amount to 1 and Profile to 0.5



Remove doubles (press the Spacebar or press Ctrlv->Remouve Doubles)


To make the first shape you describe extrude these faces: 



For the second shape you'd need to make a cut before extruding: