Yeah, that's it.
I should probably add that Slardar isn't really a hard carry, but he definitely fits within the carry category. The best description is probably that he's a timing carry, you should farm him until you hit a window where you can "out-carry" the enemy carry (amplify is completely ridiculous during a long window, probably gives you more than double the damage against most agi carries).
I guess I could write some pointers for playing him as a carry (do this after you have decided that this is the best option, if you're running 2-1-2 lanes with another carry that does physical damage you'd probably rather go some blink build).
Starting items: stout shield+branches+regen
Skill build: Max crush first, and get one rank of sprint and bash on lvl 2 and 4, then max sprint, and after that bash. Obviously picking up your ulti when you can
Core items: PTs, Magic Wand, Armlet, Helm of Dominator, BKB
Items after that: AC is usually the best option, after that whatever (satanic is pretty good).
Farm as a hard carry until you get your core items.
When you get helm of iron will+boots+stick you can start going a lot more aggressive on the lane as it provides good regen and armor, and you're probably not gonna get bursted down (you still want to get every last hit though).
It's preferably to not use crush to harass, unless you're forcing someone out of the lane, but rather to get kills; mana management is the key. If you have a strong lane partner on the lane you should be able to get kills with sprint and crush (and maybe a lucky bash), don't be too afraid to dive towers as you have quite high effective HP.
When you get your armlet and dominator, you can start doing whatever you want, usually killing the enemy carry solo repeatedly. An anti-mage without manta should die if you get amplify+crush+a bash off, amplify damage really does that much.
You still want to farm though, so you eventually get your bkb, so if you get a kill, either continue farming on the lane, tp to another lane and farm, or just do some jungling with amplify.
At this point you should also be able to force pushes, killing towers and removing map control is one of the keys to winning games as a hero as slardar.
As soon as you have gotten all outer tower, you want to push their base as you're gonna be a lot stronger than their harder carry.
Other things:
Getting roshan is easy with amplify and some help
Always carry a tp, but don't tp to help unless you're sure you will be the difference in the fight and that you'll get at least some kills, sacrificing farm early is usually not a good idea as any carry.
I probably missed a lot, apparently I need to stand in.
PTs?