Unfortunately strawberries are one of the trickier fruits to turn into jam. They don't have as much pectin as raspberries or apricots which jell in five minutes or less. Strawberries need patience. Twenty minutes on average of stirring and feeling the heat. But later you get to feel the love.
So here's how to go about it.
A quart of fresh strawberries--not the large tasteless watery ones from California--will yield four maybe five half-pints of ruby red jam. With them you will need a lime for all its juice, a pinch or two of cinnamon, a pinch of nutmeg, optionally 2 tsp of rosewater, and 1 heaping cup of sugar. Lately I've been using turbinado instead of plain white. If you are using granulated white, try to mix in a tbsp of light brown as it will add richness.
Now this is MUCH LESS sugar than commercial brands and commercial recipes call for. You cannot eliminate sugar: it is the major preservative here, preventer of an evil bacteria takeover. But lime juice is also a bacteria killer/ preservative so you can use less sugar. There will be a consequence though: once the jar is opened it will not last indefinitely the way sugar loaded commercial jam does. That's why it's sugar loaded: shelf life. Once opened, the jam must be kept in the refrigerator and eaten within 2-3 weeks. That's why I put it in small jars. ;o)
Get the jars boiling while you make the jam. You make the jam by putting all the ingredients in the tallest pot you have because when it gets hot sparks are gonna fly. You will need a spatter screen and mitts that go up your arm. You also need a long handled spoon, longer the better.
Do you cut up the strawberries? Depends on whether or not you want chunks in your jam. I recommend cutting up the large ones but not the smallest ones. I sometimes split the middle, sometimes not.
Fire up the burner and stir up the pot. Stir every minute or less. Eventually as the sugar heats up it will bubble. Stir away the bubbles. When it hits boiling, the whole mixture will rise up; you must stir it down.
If you see any foam on the surface, try to scrape it off: this is excess sugar and you don't want it in the jars. Now just keep stirring until you have thick jam. How do you know that you do? If you pull up a spoonful and it's not willing to run off the spoon but tends to stick around and drop of in clumps, you've got jam. If you run a spoon across the bottom of the pot and the jam clears a real path so you see the pot bottom, you've got jam.
You ladle the jam into the hot jars, almost but not quite to the top. Seal the jars and put them back into the boiling water bath. Water must cover them by at least 1 inch. Boil for 10 minutes. Remove and wait to hear the pop! that means they've sealed. Then cool and label and think sweet thoughts about how happy you are going to make everyone you love