Turns out the Land of Shadow is pretty darn big.
Trying to find your way to all of the Shadow of the Erdtree map fragments is part of the fun in Elden Ring's new expansion, but at a certain point you hold your hands up and admit "Yeah, I'm stuck with this." Though the main regions' map fragments are easy enough to find, in typical FromSoftware fashion, there are secret areas which are quite hard to reach.
That is, unless you're exploring every single nook and cranny you come across. Even then, if you missed a route the first time you explored an area, it's pretty hard to know where to look in terms of backtracking. That said, I'll run through how to find every Shadow of the Erdtree map fragment location, plus how to reach the region in question to grab it. This guide will, of course, feature spoilers for accessing secret areas.
The first map fragment you'll come across is in the starting area of Gravesite Plain. From where you arrive after touching the arm, head down the hill, watching out for the Curseblade enemy who drops down off an arch, then head north up the road towards the Scorched Ruins and the Furnace Golem boss in the distance. Before you reach the ruins, you'll spy the map pillar to the right of the road with the map fragment in front of it. Gravesite Plain contains notable areas like Belurat, Tower Settlement, and Castle Ensis.
The second map fragment you're most likely to find is Scadu Altus. How you do this will depend on how you arrived in the area. If you came via Castle Ensis and defeated the boss there, simply ride north up the road from Highroad Cross site of grace to find the map pillar at a fork. If you came via the Fort of Reprimand, you'll need to take a much longer road northwest, passing through the Moorth Ruins, until you reach that same fork in the road with the map pillar. The most notable landmarks in Scadu Altus are the Shadow Keep plus the Scadutree itself.
There are two ways to get into Rauh Ruins and one of them makes it much easier to get the map fragment so you know where you're going. While you can enter the upper region via the western rampart of the Shadow Keep in Scadu Altus, I recommend heading north from the Moorth Ruins until you find a cave with a Marika statue in front of it. Head through here, then through the small poison swamp with the Gravebird enemies until you reach the Ancient Ruins of Rauh. Now simply travel west along the valley with the two golems to find the map pillar on your right just before the Temple Town ruins.
The notable areas in Rauh Ruins are Rauh Base, which is the lower level, and the upper Ancient Ruins of Rauh that are only accessible via the Shadow Keep.
This area is a little trickier to find, especially as there are only two ways to get to it. The first is via the Ellac Riverbed
The alternate route is by going to the Charo's Hidden Grave area, accessible through Jagged Peak, and then dropping down gravestones set into a cliff to the Cerulean Coast West site of grace, but the way above is definitely the easiest. This is a big map fragment and covers multiple areas including Jagged Peak and Charo's Hidden Grave.
This is the most hidden area in Shadow of the Erdtree and it's quite a trek to get here. Think of it like the Haligtree from the base game. First off, you'll need to go to the Shadow Keep in Scadu Altus and find the courtyard with the flaming boats—this is on the main path through the keep from the front entrance. From there:
Now it's simply a matter of following the road from the Forsaken Graveyard grace until you reach the Woodland Trail grace. From here continue to follow the trail—if you spot the Madding Hand enemy on the road, you're going the right way. After a short while, you'll reach the Abandoned Church ruins with the map pillar just outside. The most notable location in this region is Midra's Manse.