If you have some tools at home it is relatively easy. 2 x C clamps, stones from the garden and some blocks of wood to form a frame. Here is a thread on it (as well as your own spot puncher), scan down to my post with pics so you can see what you need and it working:
This is easy to set up, make sure you lace the first eyelets so the top of the boot keeps its shape. Measure up the width of the boot before you start and as you use the clamps so you can control the amount of the stretch. I don't use heat, just time.
The downside is getting right into the toe cap area (if that is where you need to get to), the shape of the c clamps make this an issue. This is why boot stretchers use curved arms. A while ago I made another simple tool to get right into the toe cap area, you need a strap hinge, 2 round head bolts and a small length of hollow pipe (to fit over the bolts) cut to the required length (different sized boots require different lengths) and a ratchet spanner or ring spanner. pic here
https://imgur.com/a/4APhUS9
You will also need something to pack the back of the strap hinge against the heel of the boot, this is to stop the device sliding back down the boot as you begin to open it up. I also packed the sides of the strap hinge to help keep it in place.
Pretty self explanatory, cut the tube to length, slide the tube over the two bolts, fit into the boot and start winding away. I filed out the strap hinge for the bolt that has the nut on it so the bolt sat in the clamp and would not turn. This works really well, almost too well as I could see the toe cap starting to separate away from the boot. I subsequently made a clamp for the bottom of the toe cap to stop this from happening. Only downside with this is the further you get into the toe cap, the harder it is to wind the nut, you need patience, feel and time. If you just want to widen the forefoot area this would work really well.
Edit - I left a washer out that sits between the nut and the tube.