@rip_imho dont worry there's a ready supply in the Elemental Plane of Bones
@TetraspaceGrouping pray tell how to retrieve the needed components!
@rip_imho then once you've done this bootstrap up to key your mana to the plane itself its time for some classic telekinesis - yeah its through the Magevoid but the principle is the basically the same, its DC mana so this just works. use your favorite tunnel stabilisation pattern to keep law+ operating, i prefer two-loop countervorticing because it's self-stabilising but i have high mana reserves and don't need to do it that often so YMMV
@rip_imho also to clarify i'm coming at this from an arcane background, if you're divine or natural i think it works broadly the same way but definitely a good idea to check with your god
@rip_imho now next step - and this is also what the flask help you with - is just before the bones you're transporting reach the prime material you collapse the whole mana tunnel and pull it back, and re-key it from conjurative to necromantic. proper circles help a lot with this. 500 gp of directed mana capacity should be enough to ensoul the skeleton you've just summoned if it's not too scattered, and BOOM! your own undead, now try sending it some simple mental commands :)