Stir the ground flax seed into the water in a small bowl or cup and let it sit for 10 minutes to swell up.
In a large bowl, stir together the gluten-free flour blend, baking powder, and salt. Cut the cold lard or butter into small cubes and add it to the flour. Toss the cubes to coat them with the flour. Squish the butter cubes between your fingers to flatten them, or cut them into the flour with a pastry cutter or two butter knives, until the lumps are pea-sized.
Add the flax gel and the yogurt and mix it just until the flour is all moistened and the mixture is a shaggy mass. Press the dough firmly into a ball, then flatten it into a thick disk, about 1-1.5 inches thick. Wrap it in plastic food wrap, and chill it for 30 minutes (or up to 3 days). At this point the wrapped dough ball can be put into a ziptop freezer bag and frozen for up to 6 months.
Remove it from the freezer and let it warm slightly for 10 minutes. Unwrap the dough disk and cut off ⅓ of it to use for the top crust. Rewrap the smaller piece and rechill it. Shape the larger piece back into a disk and place it on the counter between 2 large squares of parchment paper. Bang it with a rolling pin to flatten it slightly, then roll it out between the parchment sheets. When it is thin enough, peel off the top parchment sheet and invert the dough onto a 9-inch deep-dish pie plate. Fit it gently into the dish, patching any cracks, then trim off the overhanging crust. Chill the crust for 30 minutes.
Preheat the oven to 425℉ (220℃).
To Fill the Pie:
In a large bowl, whisk together the sugar, liqueur (or apple juice), cornstarch, lemon juice, and salt. Gently stir in the raspberries. Set aside while you prepare the lattice strips. Roll out the pastry for the top crust (between two sheets of parchment paper if making a gluten-free crust). With a knife of rippled pastry cutter, cut ½ the dough into half-inch (1 cm) strips (you'll need 10 of them).
Scrape the raspberry filling into the chilled bottom pie crust. Dot with the butter.
Lay 5 strips, spaced evenly, in one direction over the pie. Pinch down the ends on one side to attach them to the rim of pastry around the top edge of the pie.To weave the lattice crust, flip back strips 2 and 4. Lay a new strip crosswise across the attached strips. Flip strips 2 and 4 back down, over the crosswise strip. Then flip back strips 1, 3 and 5. Place a second new strip crosswise across the attached strips, then flip strips 1, 3 and 5 back down over the new strip. Repeat with strips 2 and 4 again. Continue alternating flipped strips until you have added 5 crosswise strips and the lattice is woven over the whole pie.Press the edges of all the strips down to attach them to the crust rim around the pie. Trim off any excess pastry with a knife.
Press the tines of a fork down onto the rim all the way around the pie to firmly connect the lattice strips to the bottom crust, then trim it once more to remove any excess pastry that pushed over the edge.
Set the pie onto a larger rimmed baking sheet to catch any drips. Bake the pie on the middle rack of the oven at 425℉ (220℃) for 15 minutes, then reduce the heat to 350℉ (180℃) for another 30 to 40 minutes (for a total of 45-55 minutes).
The pie is done when you can see the filling bubbling up around the edges, and if you watch carefully, you see the slight movement of a bubble occasionally moving under the filling in the center of the pie. If the edges of the pie brown too much, cover them loosely with strips of foil.
Let cool completely before slicing, to allow the filling to set up.
Notes
You can, of course, cover the pie with a regular full pastry crust instead of a lattice top - make sure to cut plenty of slits into it.The baked pie can be cooled, wrapped, and frozen for up to 4 months. Thaw at room temperature before serving.