Here is a pattern, made by me, for size 12-18 month infant girls, flare-leg pants. These are best made out of a super stretch fabric like a jersey, knit, or fleece. This pattern can be made to accommodate a non-stretch but you will have to add extra seam allowance for that in some cases. Also, the instructions here are for refashioing adult pants to infant pants. I will post instructions later on how to use this same pants pattern to make pants from scratch using new fabric and not old clothes.
An old pair of yoga pants (or you can just use fabric!)
1" wide elastic (if you cannot salvage the elastic from the original pants)
Right-click and "Save Target As" on the following images and then print. I don't recommend printing directly from your web browser because it tends to shrink the image a little in order to put the web page information on the page.
Start disassembling the adult pants by first removing the waistband carefully. I just cut along the seam line. Also cut the tip off the knotted end of the drawstrong (if appplicable).
Note: The waistband on the adult pants had a drawstring built in that I decided to incorporate into the final design. So please keep that in mind when view these pattern instructions.
Seperate the waistband pieces. Then cut the waistband to match the pattern piece. You can use the old elastic or you can buy 1" elastic if you prefer. Basically the elastic needs to be 18" long.
Now, fold the waistband fabric in half, right-sides together, meeting the short ends together and stitch using 5/8" seam allowance. Press open allowance. Now you basically have a circle of fabric. Take the waistband fabric and fold it in half lengthwise, wrong-sides together, and press with an iron.
Take your 18 inches of elastic and sew it with a 5/8" allowance to make it a circle too. Place the elastic inside your fabric waistband all the way up to the crease, matching the seams. Set aside for now.
Cut along the inner leg seam, starting at the bottom and working your way up to the crotch. Cut the front crotch along the seam line. Now make sure the pants are perfectly folded along the exterior seam line. Smooth out the pants getting rid of any wrinkles or creases, pressing with an iron in necessary. Secure the pants near the seam line with a few pins.
At this point the adult pants should be laying down facing up, as in, the front of the pants are facing you and the tush part in touching the floor, table or whatever worksurface you are using. Keep this in mind for the remaining instructions.
Take the pattern and lay in face down on the right leg (that's your right...i.e. the adult pant leg that is closest to your right arm). Place the pattern as shown in the picture and pin through both layers of the pants.
Cut the bottom edge of the pattern and the along the inner thigh up to the crotch, stopping at the point (see image).
This is where it gets the most confusing! Seasoned sewers who have made pants before will totally understand this but it may be really confusing for a beginner. Click on the picture below to enlarge the image and see the instructions. There are several images here to clarify the instructions.
Place the pattern on the left leg now EXCEPT this time, the pattern will be facing right-side up. Repeat steps 6 and 7. You should now have two halves to a pair of pants! We're almost there!
Starting with one of the legs, turn them so that the right-sides are facing together. Match the inner thigh edges together and pin them. Stitch a 5/8" seam allowance as shown in the picture. Do the same for the other leg.
Okay, here's the next confusing part. One pant leg needs to slip inside the other, right sides together, so that you are looking at the wrong-side of one pant leg. Match up the crotch edges, pin and stitch together. It would be well advised to do a double stitch line in the crotch area for reinforcement. I have skipped that step in the past and had seams pop.
Remember to leave the top unstitched for the waist band!!!
Note: I finished the pants without taking pictures of the last few steps. So I pulled out the completed pants to take a few clarifying photos. The problem is that now my camera is possessed and is on the fritz. I was only able to get three pictures before the camera turned off and won't turn on again and those pics are super blurry. I tried to sharpen them up on the computer a bit but, I am warning you, they are pretty awful, so sorry.
Turn the pants right side out and pin the waistband to the pants, placing the waistband on the outside of the pants with the opening facing up. Match the seam of the waistband to the back seam of the pants. Sew about 3/8" from the edge.
Hem the pants to whatever length you need for the child. Trim all the excess thread and you're done! Here's what they looked like all complete: