This is a piece of dropped elk, I've already used about half of it. Normally I cut antler as I need it. In other words, the rack stays whole until I need some that way I can cut exactly what I need and save myself from cutting pieces I may not use for years. This piece is old and sun bleached, dirty with age and cracked but once it is hafted and polished it can have a look similar to bark ivory with all the deep dark fissures and snow white highlights.
If I'm cutting up a rack all at once, what I do first is cut off the crown. Leave enough material on the back to flatten it and you can make a belt buckle or sell it to someone who does.
Now, before we go any further, if you're looking to make pistol grips, for single action pistols in particular you don't want to cut the tines off immediately, you'll want to lay your grip out on the antler and see where you need to cut to get the proper piece, the best for this is usually where the first tine meets the main beam just ahead of the crown.
Now if we're just doing knife handles I normally whack off all the tines up next to the main beam
Next I deciude what I will do with the tines, this is largely dependant on what the tines lend themselves to being, long flat tines make good slabs, curved round tines will make better handles for fixed blades with hidden tangs, and some just get cast aside until a later date when I need to slab off a piece for inlay, slice for buttons ect.
This tine is pretty flat and has a straight area long enough for a set of folder slabs
I cut it where it begins to make a turn to get the longest flat piece I can
then rip it right down the middle with a bandsaw, a decent set of slabs for something about the size of a 4 1/2" knife
This tine is very round and curved.
Feels nice in the hand too
Mark it and cut it longer than needed, this will make a nice hidden tang fixed blade handle
These tines are too bent, irregular and curved to do anything with right now, though they can be used for a variety of things in the future, slice them up into buttons, use the very ends for neck knife or fire striker handles, or squeeze a single small slab out of each one later on to replace one that splits or cracks in the process of installation. This is only two tines with a few pics of each from different angles to show the irregularities
Now we get into the good stuff
The main beam takes some studying to get the most of it, if you slab a big piece like this right down the middle, you're wasting a LOT of mnaterial. If we're looking for slabs for folding knives under 6" you can get a lot more out of your antler by just shaving off the outer layer of stag. then instead of having two oversized slabs you'll have 3 or 4 properly sized slabs. I'll show you.
Find the flattest most uniform side on the beam, we'll slice that one first
It's about a 9" long piece
Cut if off and begin the slice far off center but thick enough to accomodate any knife and allow room for fitting
A nice flat slab!
Cut it about in half
A good matched set of scales for anything up to folding hunter sized with plenty of room for fitting
Now we play with the leftovers, since that was the finest set we'll get out of this antler.
Looks like I can squeeze a slab out of here about 3 3/8"
marked for cutting
remember, only cut as deep as necessary
One side down, now shave off the remaining bark for the second slab
Two nicely matched slabs with a triangular core of worthless pith. Thats 4 slabs, where you only would have gotten 2 if you had center sliced the first set.
This is pretty irregular, not flat enough in any area for a good slab. I'll toss it aside for now, I may need a piece for inlay at a later date, or with a little creative sanding and polishing could make a very unique desktop holder for a pen/pencil set. Especially a set turned out of antler!
Here's what we have, a crown for a belt buckle, 3 sets of slabs, a "carver" round for a hidden tang, and some extra for other crafts later on. If you don't do other crafts like belt buckles and pen/pencil holders and such any scrap can be sold to folks that do. So very little goes to waste.
There it is, I hope you found it helpful. The best advice I can give is know what you want out of it and read the angles of the stag and slice accordingly. If you want something particular like a set of grips for a single action pistol, you may have to sort through several racks to find a piece that is suitable. You can't pull a rabbit out of a hat every time.
I set up a tall fence on my bandsaw after that and still don't get as straight of a cut as you did there. 
