I suppose you have a testfor command that tests if both a dropper and a crafting table are on the ground.

What I suggest you do is run an execute command at either of the two items, and test of the other item is nearby:

/execute @e[<firstItem>] ~ ~ ~ testfor @e[<secondItem>,r=<distance>]

As you can see, I added r= to test only for entities in a certain radius (if you need the items to be 3 blocks or closer to each other, type r=3, and so on.). You can then put the command into a command block and lead a comparator out of it that would execute the command for custom crafting.

Because you already had half the thing working, I figured out you already found out a method of testing for specific items. An example can be found here, just in case.

I suggest you have a testfor command that tests if both a dropper and a crafting table are on the ground.

What I suggest you do is run an execute command at either of the two items, and test of the other item is nearby:

/execute @e[<firstItem>] ~ ~ ~ testfor @e[<secondItem>,r=<distance>]

As you can see, I added r= to test only for entities in a certain radius (if you need the items to be 3 blocks or closer to each other, type r=3, and so on.). You can then put the command into a command block and lead a comparator out of it that would execute the command for custom crafting.

Because you already had half the thing working, I figured out you already found out a method of testing for specific items. An example can be found here, just in case.