It seems as though from underneath there is not a way to get at it.
I'm no mechanic either so here's what may happen. The temps will go down to 0°F just before you're ready to do it. There will be snow or mud under the truck so you'll find a cracked piece of plywood that will leak and eat your tools. Just as you're on your knees sliding it under, you'll bring your head up fast and crack it on the bumper so you get to do the job in some discomfort.
Battery dis-connect is simple enough but a corroded wire will break as you're undoing it so you'll call a buddy and take the first ride to the parts store. You've thought about everything you need, buy more, then go back at it. Once you're laying under the truck without your safety glasses, you'll align your eyes directly under the first bolt and put your wrench on it. The oily, greasy chunks will release and fall directly in your eye. You'll scatter out from under the truck and bang your head on the exact same spot you did before.
Once your eyes are cleaned you'll slide underneath again, only to realize that you took your wrenches out with you....and this time you carefully slide out from under the truck, put your tools in a tray, and slide under again.
Now, to get started, your safety glasses in place, laying on your back you lift your arms up to start wrenching. The pain in your shoulder stops you for a minute so you lower your arms. That was good timing because your phone will ring.......and it's the wife. Being the safe people we are we don't take the phone under the truck so you push yourself out again, smack your head and just as you reach for the phone, she'll hang up. You want call her back because she'll worry so 30 minutes later, you take your phone under the truck and try to remove the first bolt with one hand.
Once the bracket bolt is out and the first big bolt rolls into the mud, you're ready for the somewhat heavy starter to fall and pinch your hand on the exhaust or frame rail. Remove the last bolt and don't worry, It's just a flesh wound, hurts like heck and there's grease in it, but you're nearly done.
In the dark and shadows of the wee area between the top of the starter and the engine, lay the 1st nuts you'll put on when you re-install the starter. I try and remember where they come off, but a guy is upside down, it's dark and the head hurts. Typically, the wires are long enough that you can adjust the dismounted starter and reach the big wrench into the wee void to try and undo the main power wire. The second that big wires comes off, the starter will fall pinching your hand again and straining the small wire that is clearly the brain of the operation. With the tiny nut jammed between the housing and the tension of the wire, you'll lift it with one hand and make 57 turns of the wrench with the other, missing the target nut every second time. The nut is small and it will fall on the nut eating plywood and you'll call your buddy for a second trip to the parts store. You never expected to lose your nut over a small job like this.
With one final pop, it's free. Not free of the truck, just free of it's bolts and wires. You'll wiggle it, turn it, pull it, lift, wiggle, turn and not until you've been distracted by a car driving by and turn your head, will it be yours. At that moment the starter is free and crashes down on your safety glasses ramming them into the bridge of your nose but sparring your bruised cranium. The relief is grand as you roll the starter off your chest and down onto the metal tool tray.....with just the tip of your pinky finger between the crushing surfaces.
All that's left is sliding out from under the truck,........ but you'll pause for a second, close your eyes and be thankful that this was just another easy task.