You'll need a small sheaf of corn stalks. (A note to my US readers: that's wheat to you. What you call corn, we call sweetcorn. And you can make dollies with them but they're very different.)
If possible, ask permission of the landowner before you gather anything. Always make sure you gather from the edges of the field where the harvester can't reach and the grain will go to waste. Don't take more than you need. A bundle the size of the one in the photo is plenty for three or four dollies. Use your corn fresh. If you let it start to dry out it will be difficult to work and will crack easily.
Gather up a handful of stems. If you want to be proper about it, make sure that you have an odd number. You must have at least 5 stems to weave and you'll find it much easier if you have a further 6-8 to act as the core. If you're superstitious about the number 13 make it 6 or 10! Tie the bundle with pale-coloured cotton or thread near the base of the corn heads. Gently pull on each stem to ensure you have a neat bunch and that there are no straggly ones.
This is the only complicated bit. Honest. Select four sturdy-looking stems and bend each one outwards to form a cross. (Like in the photo. We'll call them A, B, C and D, starting with the one closest to you and working anticlockwise around the bundle.) Then select another stem (we'll call it E) and bend it down to run parallel to A. If you look closely at the photo you'll see there's a fifth stem under my thumb.
OK. Gently take hold of A and fold it over E to lie parallel with B. This will secure E in place. Now take B over A and bend it to lie parallel with C. Continue like that, keeping the basic cross shape of the stems and slowly turning the dolly round as you go. You'll find a woven shell forming around the core. Keep going until the stems are almost used up. You'll find you can put the dolly down without it unravelling as long as you are careful.
If you don't want a very short dolly you'll need some extension stems to continue working with. Cut the heads off a number of stems (an extra 10 or 15 is probably about right. Remember you're working in groups of 5) and keep them handy.
When you need to extend one of the stems slip the thin end of a new stem into the hollow end of the one you've already worked. You might find you need to trim the end of the old stem. If you adjust the joins correctly you'll find that the next bend in the stem will hold the inner piece in place.
Once your dolly is as long as you want it to be you can trim off the excess neatly as shown.
Now you need to form the "handle". If you can plait with five stems use them all to create a "ribbon" emerging from the top of your dolly. If you can only plait with three, that's fine. Just ensure that you include the last stem you bent over so that you lock the others in place.
This is another tricky bit. Bend the ribbon over into a loop and secure it in place by threading the cut ends of the straws through the loops formed by your weaving. You might need to ease some of the loops open slightly to do this.
Then all that's left to do is neaten up any stray bits. Careful when you trim them that you don't accidentally cut any of the weaving. Finish off your dolly by tying a pretty ribbon near the corn heads to cover up the thread you used to tie them together.