I can imagine my iPod flying through the air and crashing hard against the wall if I were to try that.There are retainer clips that have to be released with a thin spatula blade-like tool that is inserted into the very small gap between the two halves of the clamshell.
Many people struggle with this aspect alone, as you have to go around the entire enclosure releasing each clip and then with the one hand holding the iPod exert some slight continuous pressure in pulling each half away from the other, otherwise when you move around the enclosure with the tool, releasing another clip manages to just re-engage the one you just released two clips back. It's an annoying juggling act and obviously a design choice meant to stymie novice attempts at opening the unit at all. Most people would just give up.
This is compounded (and proven to be deliberate by Apple) by the fact that they made each successive version of iPod harder to open than the previous. So a Gen. 5, while annoying, is nowhere near as difficult to open as the Gen. 6 was despite them looking pretty similar, and the Gen. 7 was even a bit tougher still to crack. It requires patience unless you plan to replace the rear metal half, because you will bend and ripple the edge of the metal if you try to shortcut the process and get too heavy handed with the tool, and that leaves the unit looking shabby or in need of a new rear cover.
The good news is the rear cover is not expensive, and the ones you can get on eBay even have the large capacities of 128, 256, 512GB, or even 1TB laser etched on them, to signify the modded iPod's new capacity.
However there is one more gotcha designed in by Apple, and it's the biggest one of all, once again proving just how deliberate they were in not wanting people to repair or upgrade an iPod.
Once you've hassled with the two case halves and the blade tool enough to get the two halves apart, the tendency or human nature is to immediately fully pull apart and separate the two completely... YES... SUCCESS... er, NOT! You see they glue the battery and its fragile ribbon cable to the rear of the case, and that cable has insufficient slack unless it is first released from the logic board, you can only separate the two halves about .5" before you run out of slack. No problem right, after all you are likely replacing that battery anyway as part of the restoration, you wouldn't go to all that trouble and not install a new battery, who cares if you tear the ribbon cable? Apple made sure the battery ribbon cable is actually very strong. It does not tear, rather, you end up tearing the retainer clasp straight off of the logic board, ruining it unless you can do microsurgery with a hot air station to remove the broken connector and install a new one with solder paste. Alternatively, you could insert the new battery cable and then just put a blob of hot glue on the connector, knowing that's the last new battery the unit will ever receive.
The site where I bought the flash memory conversion adapter boards goes out of their way to warn people of this huge gotcha designed in failure waiting to happen, and I for one never ruined a logic board by carefully heeding that warning. LOADS of others were too hasty, ignored the warning, and ruined their iPod by destroying the battery cable connection point.
So once you've wrestled with the case to get it open, you can only separate the two halves .5", before needing to then hold them in one hand, while the other maneuvers a plastic fine tip spudger tool inside and gently releases the clasp that affixes the battery cable to the logic board. Only then can you safely separate the two halves and even then, there is still one other ribbon cable for the connection of the headphone jack to the logic board, but it has sufficient slack to allow the two halves to be safely separated and placed alongside each other without destroying anything.
The above is actually the hardest part of the modification, removing the HDD and installing the flash memory adapter and new battery is simple by comparison, but you then juggle one last time in lining up the new battery's ribbon cable into the connection point, and snugging down it's clasp. You don't dare then click all of the case retainer clips fully closed/buttoned up until you have first confirmed the unit powers ON, and also Restores properly on connection of the USB cable and launch of iTunes. Once that's done, you can finally click the two halves together and finish it.