Easy-peasy apron for kids that will grow with them, but make it a bit larger and grown-ups can use it too.
Cut out a pocket in any shape (rectangular is easiest.) Then hem the top of it and turn under the edges all the way around. Note: If making a curved pocket like this one, cut into the fabric at the curves nearly to the fold before turning the fabric under - this will give a smooth curve.
Sew trim to the pocket, then pin the pocket in place on the large piece of cotton fabric that makes up the bottom of the apron. (Notice I didn't even change the thread in my machine to red when I stitched on my trim - hasty, hasty.) Top stitch the pocket on (leaving the top open - pockets are more useful when you can put things in them. Sew close to the edge of the pocket - 1/8" or 2-3 mm.
Make the neck strap and the waist ties (or just the neck strap if using twill tape for the ties.) Sorry no photo for this - it's very easy though. Take the 10cm x 65cm strip of fabric and fold the 10cm edges inside so the fabric meets in the middle and press all the way down the strip.
Then fold it again and iron creating a 2.5cm x 65cm pressed strip. Top stitch it closed all the way down the length of the strip close to the edge, then top stitch the other edge all the way down.
NOTE: If you aren't using twill tape for the ties, repeat this strap making process using a 10cm x 100cm strip of fabric then cut it into two 50cm long pieces.
Take the 30cm x 25cm piece of fabric. Fold under and press a 1cm hem on the 25cm edge. Slide the neck strap under the fold about a 2cm from the edge of the fabric. Hold the strap under the pressed edge then fold it up and over the edge. Now, while still holding the strap under the fold, hem the edge attaching the strap at the same time.
Measure the strap around child's neck and mark the placement for the buttonholes. Put in three buttonholes, the first one should fit now and two closer to the end of the strap are to adjust as the child grows. Now roll the end of the strap over twice and sew it down to hem it.
Hem up the remaining edges (5mm hem - about 1/4 inch) of the upper piece of the apron. Then attach a button to the opposite side of the strap. NOTE: The button could be place on the inside or as detailing on the outside of the apron.
Take the larger piece of cotton and hem the top edge of it. Then take your twill tape, or the fabric ties and hem them into both top, side edges of the bottom section just like the process for the neck strap.
Place the top section of the apron above the bottom section, then turn it over and center it on top off the bottom section. The two parts should now be top to bottom with right sides of the fabric facing each other. Sew the two sections together.
The very simple construction should look like this. As a final optional step, you could turn the apron over and top-stitch across the bottom edge of the top section of the apron, this helps it lay smoothly - I have done this.