Probably the most common mistake beginning handquilters make is to draw the quilt sandwich drum tight in the hoop. You should actually have enough "give" in the hoop to equal a fist -- maybe 4 to 6 inches. This is what allows you to manipulate the layers onto the needle.
Here is a link to my favorite lap hoop:
http://www.keepsakequilting.com/productdetail/9113.htm
The swivel ball allows you to adjust the angle easily, and there is nothing to impede the hand underneath.