First generation Sonoma's were under the dash in the fuse panel. 94-97 are under the radio, 98 and up are behind the glove box.
Remove the two kick panels under the dash board on the passenger side. There will be one in the center of the truck and another one on the passenger side. There are six 7mm bolt's that hold on the kick panels on.
The panel in the center may have the optional 12V accessory plug ins, this you will not have to remove simply let panel hang out of the way. When the kick panels are out, then you can then remove the three 7mm bolt's holding on the glove compartment door.
Once removed the flasher is now exposed. It is on the right side of a wiring distribution block if it's still as it was from the factory there will be a green strap that will be holding it in it's socket.