How to create a delay in Minecraft without repeaters? [duplicate]

For delays of order of 30 seconds to 4 minutes the Etho Clock is the optimal solution. You fine-tune the time by changing the number of items in the hopper, one item corresponding to 0.8s. If you want just delay instead of cyclic operation, you can use this in pulse extender variant - one of the pistons sticky, one normal (the clock variant uses both sticky pistons).

In case this isn't visible: the hoppers are facing into each other.

Let a minecart fall through one or several cobwebs. Falling through a single cobweb takes about 25 seconds. A circular track let you loop. A detector rail let you activate a redstone signal.