<font _mstmutation="1">Hello, you can put all the required components in the "top layer", check out the tutorial here if you don't know how to do it.</font> 

 But the same tutorial page say 'route the track and copper on the bottom layer.' why not top layer? <br> <br> <br> <br>

@vu3dxr, Single sided PCBs predated double sided and come from a time long before surface mount components. Therefore through hole components were inserted from the top side of the board and soldered to the tracks on the bottom layer. Layer on, wave soldering required that the pads were on the bottom of the PCB even if it was a 2 layer PCB with plated through holes. For manual soldering it is easier to insert through hole parts from the top and solder the bottom layer and also to put any surface mount parts on the bottom layer too. <br> If you do not need a single layer board then why not design it as a 2 layer and get JLCPCB to manufacture the PCB. It'll come out as a professional quality board with through plated holes, silk screen and solder mask. Much nicer to work with than hand etched boards. :)