I want to install a STRONG shelf on my garage wall about a foot
above the floor. The shelf will be on the wall between the garage
and the house.

I plan to attach a 2 by 4 to the wall with lag bolts into the bottom
plate of the wall. The back of shelf will sit on the 2 by 4
attached to the wall and the front will sit on another 2 by 4
supported by 2 by 4 legs.

(The garage floor is about a foot below the finished floor of the
house which is above the crawlspace. I live in an frost-free area
so I do not have a basement. The bottom foot of the wall in the
garage is concrete.)

I want to attach 2 by 4 cross pieces to the front and back 2 by 4's
with joist hangers about every 16 inches. I plan to attach the legs
to the front 2 by 4 with upside-down joist hangers. I will use
drywall screws to fasten the joist hangers to the 2 by 4's. I will
use the largest particle board shelf I can find at Home Depot or
Lowes as the top of the shelf. I think I have seen some that are 8
feet by 16 inches by about 0.75 inches thick.

Does what I have described sound like a good plan? Can you think of
anything I could change that would make the shelf easier to make, or
less expensive? Thank you in advance for any help.
--
When I am in the kitchen, I often kick one of my cat's balls.
After I kick it, he will sometimes play with it for a few
seconds to several minutes. His favorite are the ones that
rattle. He'll play with any ball that makes noise.