The bottom line is this. A lot of the information on bombs online is rubbish. Terrorists tend to make two types of bombs; ANFO and AP. The instructions are easy to find, the materials easy to get, and the manufacturing very simple.
I would have to disagree with that. The vast majority of IEDs has not been Ammonium Nitrate Fuel Oil (ANFO). Such a device requires far too much raw material and no place to hide a 50 gallon drum along a dirt road.

Where I am and have recently been, most have been modified projectiles without fuses, or simple command detonated IEDs with extracted HEs from projectiles.