Let's take a look at the Minecraft Wiki articles on directional blocks.

Pistons:

Pistons are always placed facing toward the player. When powered...

Droppers:

A dropper can be placed so that its output faces in any direction, including up or down. When placed, the dropper's output faces toward the player.

Dispensers:

A dispenser can be placed so that its output faces in any direction, including up or down. When placed, a dispenser always faces the player placing it.

Unfortunately, what you have requested is not possible in Vanilla Minecraft. You could try creating a complicated command-gadget for this or download a mod that would do the trick, but those are entirely different topics for entirely different posts.

If you're in Java Edition and building in Creative Mode and need to get inside your redstone contraption at the right angle to place your directional blocks, you can press F3+N to switch to Spectator Mode, fly into the redstone contraption, press it again to switch back to Creative, and place the block facing the correct way.