I use these. https://www.omega.com/en-us/control-.../p/SSRL660DC50
They are more expensive, but have zero crossing, and no noise or flyback; which helps a lot...
Super simple to wire up.
This is just for path illustration though, don't make a suicide cord, it MUST be properly wired to the BACK of the to->amp wallsocket in a grounded box (or a plastic box).
I'd recommend a metal box big enough to stuff all the wires into it and for heatsinking the relay; and in that case the green ground MUST be attached to the metal box as well for safety reasons (as well as to the frame of all involved wallsocket boxes as-applicable).
make SURE the hot and neutral don't touch anything else!
and make SURE the fuse holder isn't grounded to the case (because it will blow).
NEVER change the fuse when it is plugged in because the fuse holder is HOT (in case that wasn't obvious).
NEVER service it when it is plugged in (in case that wasn't obvious).
When plugged in, consider anything in-line with the hot or neutral wires as HOT, as they are both current-carrying conductors.
Only grounded metal is safe, ungrounded metal is potentially unsafe (and by grounded I mean connected to the main panel ground-neutral bonding jumper and grounding electrode via the "green" ground wire.)
The ground wire only ever carries line-power under an extremely rare/brief fault condition, and since it is bonded to the neutral leg at the mains service panel, the current will return to the breaker via the meter/pole transformer's hot leg, tripping it from excessive current draw beyond its rated value. The mains breaker won't even "care" because it is rated for 100-200A (a much higher trip-value.)
For extra safety GFCI's can be used on both wallsockets.
This way if any of the current from the hot or neutral tries to reach ground via any alternative paths (say: through a person) it will trip at the upstream plug before reaching dangerous levels.
It is recommended to test GFCI's every few months or when they are suspect. Especially in bathrooms, kitchens, but also garages and outdoor plugs too. Basically anywhere humans and water and electricity can come in contact. They should turn off when the test button is pressed. If not, they MUST be replaced with a new one ASAP.
I'd recommend a fuse on each side of the relay just for "extra" safety as well...
The relay is always-hot on the breaker-side, best to unplug it when going on vacations; mostly just for extra safety, there is a few microvolts and microamps of continuous pass-through that doesn't do anything (unless the relay gets hit with a surge when you aren't around).
The same relay can be used for a 15A or 30A wallsocket, with appropriate fuse & wire gauge and plugs/cords.
But if you are gonna push 30A+ through it you might want to buy the heatsink that goes with it.
It has a green LED when it is conducting (i.e. on)