New to pigs, need help planning

Ok, so last year my dear husband and I moved onto our now 10 acres. We're selling two acres of our former 12 ares to friends who want to partially homestead as well, and we're moving on from our rabbits and chickens into the bigger livestock.  

The first/second type of animal we're going to bring in are pigs.  (We might get our cattle first, but that's another issue, lol!)  I have available concrete blocks to build a pig pen.  The area is sloping east with a large area, but not a ton of blocks, perhaps two or three pallets worth?  These are being recycled from another project from our last house and they are the only things I have to work with.  My plan is to build a 4 foot wall in a rectangle shape with the lower, East side wall having a gate.  The West side will have a smallish? area with a block floor and roof, (from North wall to South wall) and at least two thirds of the pen will have bare ground for rooting/wallow building, etc.  I plan on using hay/straw from our land to put onto the concrete floor area for bedding.

Any suggestions on size for two pigs?  Depth of the blocks below ground with a 2 foot freeze depth?  Yes, I know they like to root down under walls, so hopefully 6 foot of concrete blocks total in the wall will help?  Do I need to go deeper?  There's no pasturage, although I might start/finish them in my garden but only after teaching them about electric fencing which I won't have anytime soon.  I plan on butchering in the fall, perhaps getting 4 piglets and butchering two small (100 pounds?) and letting the other two go until winterish weather sets in? Our first snow comes at the end of November, but really it doesn't snow until Jan/Feb.  I have two large freezers and plan on smoking/drying at least most of the meat.

Thanks for any suggestions!

Annette

Much will depend on the breed of pig. Have you decided? What zone are you in?

The piglets around here are typically bacon type mixes, no specific breed, and we're in zone 6a, Missouri around Springfield area on the plains.  Most of our winds come from the North/South/West, rarely from the East which is why I'm situating the pen gate on that side.

Although I have never had the experience, I always consider how I will move the animal if it should die in the shelter. Also, having a roof that can be removed makes the pen much easier to clean.

Big gate (probably about 6 feet) and a roof of welded wire and a tarp is what I'm planning on.  There's pasture right next to the pen area so I can move a truck in there as well.