05AB1E, 8 bytes
X®‚xâ˜Â«
X push an integer variable, which is initialized to 1 (using 1 makes it a string, which makes the output look weird)
® push the register, which is initialized to -1
‚ pair, to get [1, -1]
x push tos and itself doubled, to get [1, -1], [2, -2]
â Cartesian product, all pairs
˜ Flatten, to get a list of coordinates instead of a list of pairs
 Push tos and itself reversed
« Concatenate